Spring interconnect structures

ABSTRACT

An interconnection element of a spring (body) including a first resilient element with a first contact region and a second contact region and a first securing region and a second resilient element, with a third contact region and a second securing region. The second resilient element is coupled to the first resilient element through respective securing regions and positioned such that upon sufficient displacement of the first contact region toward the second resilient element, the second contact region will contact the third contact region. The interconnection, in one aspect, is of a size suitable for directly contacting a semiconductor device. A large substrate with a plurality of such interconnection elements can be used as a wafer-level contactor. The interconnection element, in another aspect, is of a size suitable for contacting a packaged semiconductor device, such as in an LGA package.

RELATED APPLICATIONS

This application is continuation-in-part of patent application Ser. No.09/205,022 filed Dec. 2, 1998 entitled “Lithographic Contact Elements,”and patent application Ser. No. 09/205,023 filed Dec. 2, 1998 entitled“Lithographic Contact Elements.”

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to an interconnection (contact) element suitablefor effecting pressure connections between electronic components and isparticularly useful for contacting semiconductor packages or forcontacting a semiconductor directly.

2. Description of Related Art

Interconnection or contact elements may be used to connect devices of anelectronic component or one electronic component to another electroniccomponent. For example, an interconnection element may be used toconnect two circuits of an integrated circuit chip or including anapplication specific integrated circuit (ASIC). Interconnection elementsmay also be used to connect the integrated circuit chip to a chippackage suitable for mounting on a printed circuit board of a computeror other electronic device. Interconnection elements may further be usedto connect the integrated circuit chip to a test device such as a probecard assembly or other printed circuit board (PCB) to test the chip.

Generally, interconnection or contact elements between electroniccomponents can be classified into at least the two broad categories of“relatively permanent” and “readily demountable.”

An example of a “relatively permanent” interconnection element is a wirebond. Once two electronic components are connected to one another by abonding of an interconnection element to each electronic component, aprocess of unbending must be used to separate the components. A wirebond interconnection element, such as between an integrated circuit chipor die and inner leads of a chip or package (or inner ends of lead framefingers) typically utilizes a “relatively permanent” interconnectionelement.

One example of a “readily demountable” interconnection element is theinterconnection element between rigid pins of one electronic componentreceived by resilient socket elements of another electronic component,for example, a spring-loaded LGA socket or a zero-insertion forcesocket. A second type of a “readily demountable” interconnection elementis an interconnection element that itself is resilient or spring-like ormounted in or on a spring or resilient medium. An example of such aninterconnection element is a tungsten needle of a probe card component.The interconnection element of a probe card component is typicallyintended to effect a temporary pressure connection between an electroniccomponent to which the interconnection element is mounted and terminalsof a second electronic component, such as a semiconductor device undertest.

With regard to spring interconnection elements, generally, a minimumcontact force is desired to effect reliable pressure contact to anelectronic component (e.g., to terminals of an electronic component).For example, a contact (load) force of approximately 15 grams (includingas little as 2 grams or less and as much as 150 grams or more, perterminal) may be desired to effect a reliable electrical pressureconnection to a terminal of an electronic component.

A second factor of interest with regard to spring interconnectionelements is the shape and metallurgy of the portion of theinterconnection element making pressure connection to the terminal ofthe electronic component. With respect to the tungsten needle as aspring interconnection element, for example, the contact end is limitedby the metallurgy of the element (i.e., tungsten) and, as the tungstenneedle becomes smaller in diameter, it becomes commensurately moredifficult to control or establish a desired shape at the contact end.

In certain instances, spring interconnection elements themselves are notresilient, but rather are supported by a resilient membrane. Membraneprobes exemplify this situation, where a plurality of microbumps aredisposed on a resilient membrane. Again, the technology required tomanufacture such interconnection elements limits the design choices forthe shape and metallurgy of the contact portion of the interconnectionelements.

Commonly-owned U.S. patent application Ser. No. 08/152,812 filed Nov.16, 1993 (now U.S. Pat. No. 5,476,211, issued Dec. 19, 1995), and itscounterpart commonly-owned co-pending “divisional” U.S. patentapplication Ser. No. 08/457,479 filed Jun. 1, 1995, U.S. patentapplication Ser. No. 08/570,230 and U.S. patent application Ser. No.09/245,499, filed Feb. 5, 1999, by Khandros, disclose methods for makingspring interconnection elements. In a preferred embodiment, these springinterconnection elements, which are particularly useful formicro-electronic applications, involve mounting an end of a flexibleelongate element (e.g., wire “stem” or “skeleton”) to a terminal on anelectronic component, coating the flexible element and adjacent surfaceof the terminal with a “shell” of one or more materials. One of skill inthe art can select a combination of thickness, yield strength, andelastic modulus of the flexible element and shell materials to providesatisfactory force-to-deflection characteristics of the resulting springinterconnection elements. Exemplary materials for the core elementinclude gold. Exemplary materials for the coating include nickel and itsalloys. The resulting spring interconnection element is suitably used toeffect pressure, or demountable, interconnections between two or moreelectronic components, including semiconductor devices.

Commonly-owned, co-pending U.S. patent application Ser. No. 08/340,144,filed Nov. 15, 1994 and its corresponding PCT Patent Application No.PCT/US94/13373, filed Nov. 16, 1994 (WO95/14314, published May 16,1995), both by Khandros and Mathieu, disclose a number of applicationsfor the aforementioned spring interconnection elements, and alsodisclose techniques for fabricating tip structures at the ends of theinterconnection elements. For example, a plurality of negativeprojections or holes, which may be in the form of inverted pyramidsending in apexes, are formed in the surface of a sacrificial layer(substrate). These holes are then filled with a contact structurecomprising layers of material such as gold or rhodium and nickel. Aflexible elongate element is mounted to the resulting tip structure andcan be overcoated in the manner described hereinabove. In a final step,the sacrificial substrate is removed. The resulting springinterconnection element has a tip structure having controlled geometry(e.g., a sharp point) at its free end.

Commonly-owned, co-pending U.S. patent application Ser. No. 08/452,255,filed May 26, 1995 and its corresponding PCT Patent Application No.PCT/US95/14909, filed Nov. 13, 1995 (WO96/17278, published Jun. 6,1996), both by Eldridge, Grube, Khandros and Mathieu, discloseadditional techniques and metallurgies for fabricating tip structures onsacrificial substrates, as well as techniques for transferring aplurality of interconnection elements mounted thereto, en masse, toterminals of an electronic component.

Commonly-owned, co-pending U.S. patent application Ser. No. 08/788,740,filed Jan. 24, 1997 and its corresponding PCT Patent Application No.PCT/US96/08107, filed May 24, 1996 (WO96/37332, published Nov. 28,1996), both by Eldridge, Khandros and Mathieu, disclose techniqueswhereby a plurality of tip structures are joined to a correspondingplurality of elongate interconnection elements that are already mountedto an electronic component. Also disclosed are techniques forfabricating “elongate” tip structures in the form of cantilevers. Thecantilever tip structures can be tapered, between one end thereof and anopposite end thereof. The cantilever tip structures are suitable formounting to already-existing (i.e., previously fabricated) raisedinterconnection elements extending (e.g., free-standing) fromcorresponding terminals of an electronic component.

Commonly-owned, co-pending U.S. patent application Ser. No. 08/819,464,filed Mar. 17, 1997, by Eldridge, Khandros and Mathieu, representativelydiscloses a technique whereby a plurality of elongate interconnectionelements having different lengths than one another can be arranged sothat their outer ends are disposed at a greater pitch than their innerends. The inner, “contact” ends may be collinear with one another, foreffecting connections to electronic components having terminals disposedalong a line, such as a center line of the component.

As electronic components get increasingly smaller and the spacingbetween terminals on the electronic components get increasingly tighteror the pitch gets increasingly finer, it becomes increasingly moredifficult to fabricate interconnections including spring interconnectionelements suitable for making electrical connection to terminals of anelectronic component. Co-pending and commonly-owned U.S. patentapplication Ser. No. 08/802,054, titled “Microelectronic ContactStructure, and Method of Making Same,” discloses a method of makingspring interconnection elements through lithographic techniques. In oneembodiment, that application discloses forming a spring interconnectionelement (including a spring interconnection element that is a cantileverbeam) on a sacrificial substrate and then transferring and mounting theinterconnection element to a terminal on an electronic component. Inthat disclosure, the spring interconnection element is formed in thesubstrate itself through etching techniques. In co-pending,commonly-owned U.S. patent application Ser. No. 08/852,152, titled“Microelectronic Spring Contact Elements,” spring interconnectionelements are formed on a substrate, including a substrate that is anelectronic component, by depositing and patterning a plurality ofmasking layers to form an opening corresponding to a shape embodied forthe spring interconnection element, depositing conductive material inthe opening made by the patterned masking layers, and removing themasking layer to form the free-standing spring interconnection element.

Co-pending and commonly-owned U.S. patent application Ser. No.09/023,859, titled “Microelectronic Contact Structures and Methods ofMaking Same,” describes an interconnection element having a base endportion (post component), a body portion (beam component) and a contactend portion (tip component) and methods separately forming each portionand joining the post portion together as desired on an electroniccomponent.

Co-pending and commonly-owned U.S. patent application Ser. No.09/107,924 and its parent, U.S. Pat. No. 5,772,451 issued Jun. 30, 1998,both entitled “Sockets for Electronic Components and Methods ofConnecting to Electronic Components,” show a socketing device for matingto a packaged semiconductor.

What is needed is a method of fabricating interconnection elementssuitable for present fine-pitch electrical connections that is scalablefor future technologies. Also needed are improved methods of makinginterconnection elements, particularly methods that are repeatable,consistent, and inexpensive.

SUMMARY OF THE INVENTION

An interconnection element is disclosed. In one embodiment, theinterconnection element comprises a spring (body) comprising a firstresilient element with a first contact region and a second contactregion and a first securing region, and a second resilient element witha third contact region and a second securing region. The secondresilient element is coupled to the first resilient element throughrespective securing regions. The second resilient element is positionedsuch that upon sufficient displacement of the first contact regiontoward the second resilient element, the second contact region willcontact the third contact region.

The interconnection element of the invention is suitable for makingeither temporary or permanent electrical connection between terminals ofan electronic component such as a PCB and a semiconductor chip. Formaking temporary connection, the electronic component interconnectionelement of the invention may be coupled to a substrate such as anelectronic component and the electronic component may be broughttogether with another electronic component so that the one end of theinterconnection element is in pressure contact with contact pad or aterminal of the other electronic component. The interconnection elementreacts resiliently to maintain contact pressure and an electricalconnection between the two components. For making a permanentconnection, the electronic component upon which the interconnectionelement is coupled may be brought together with another electroniccomponent and an attachment element of the interconnection element isjoined or bonded, such as by soldering, welding, or brazing or with aconductive adhesive, to a terminal of the other electronic component. Inone embodiment, the interconnection element is compliant and mayaccommodate differential thermal expansion between the two electroniccomponents.

By fabricating a body of the interconnection element with a plurality ofresilient elements, the mechanical properties of the interconnectionelement are improved over single beam spring interconnection elements,particularly in fine pitch spacing ranges of current and futuretechnologies of contacts or terminals of an integrated circuit. This isuseful for mating to a packaged semiconductor as in a socket for an LGAor BGA packaged device. This also is useful for mating directly to asemiconductor as in a chip-scale packaging application. In addition,this is useful for other chip-scale contacts such as probing asemiconductor device on a wafer. For example, the multiple resilientelement (e.g., multiple-leaf) body of the interconnection element of theinvention offers improved mechanical properties such as a higher springconstant, improved compliance, and lower material stress over similarlysized single beam spring interconnection elements in sub-micronapplications.

An electronic component is also disclosed. In one aspect, the electroniccomponent comprises a plurality of interconnection elements, coupled toa substrate and configured in a relation to contact an array of contactpads of a chip-scale device, each interconnection element comprising afirst resilient element and second resilient element. The firstresilient element includes a first and second contact region and asecuring region. The second resilient element includes a third contactregion and is coupled to the first resilient element through respectivesecuring regions. The second resilient element is positioned such thatupon sufficient displacement of the first contact region towards thesecond resilient element, the second contact region will contact thethird contact region. The plurality of interconnection elements arearranged, for example, in an array to accommodate the connection orcoupling of the interconnection elements with, for example,corresponding contact pads or terminals of a second electroniccomponent.

An electronic component according to the invention is particularlysuitable for making temporary or permanent electrical connection with asecond electronic component having “fine-pitch” contact pads orterminals, for example, spacing of at least less than 5 mils (130 μm),such as 2.5 mils (65 μm). As will be evident from the description thatfollows, minimized pitch between interconnection elements of anelectronic component of the invention is achieved in part by modifyingthe thickness of the body or spring portion of the interconnectionelement of the electronic component. Instead of a single beam body, theinterconnection elements of the electronic component are comprised of aplurality of resilient elements to improve the mechanical properties ofeach interconnection element. A desired spring constant of multiple,coordinated springs reinforce and support the primary spring andinterconnection element (e.g., tip). A leaf portion body also improvesthe compliance of the body at a reduced material stress. Applications tolarger scale devices, including, for example, devices with contactpitches of about 50-100 mil (1.3-2.6 mm) and even larger are feasible aswell.

Other embodiments, features, and advantages of the invention will becomeapparent in light of the following description thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

The features, aspects, and advantages of the invention will become morethoroughly apparent from the following detailed description, appendedclaims, and accompanying drawings in which:

FIG. 1 is a cross-sectional side view of an example of aninterconnection element having a single beam spring coupled to anelectronic component.

FIG. 2 shows the interconnection element of FIG. 1 in contact with asecond electronic component.

FIG. 3 is a cross-sectional side view of an example of aninterconnection element having a spring of multiple leaf portionscoupled to an electronic component.

FIG. 4 shows the interconnection element of FIG. 3 in contact with asecond electronic component.

FIG. 5 is a graphical representation of the force applied to asingle-beam interconnection element and a leaf-portioned interconnectionelement, respectively, versus deflection distance of the interconnectionelement.

FIG. 6 shows the material stress for a single-beamed interconnectionelement and a leaf-portioned interconnection element, respectively,versus deflection distance of the interconnection element.

FIG. 7 is a cross-sectional side view of a structure having atriangularly-shaped feature formed in a surface of a substrate withconductive layers overlying a surface of the substrate and thetriangularly-shaped feature in accordance with an embodiment of formingan interconnection element of the invention on a sacrificial substrate.

FIG. 8 shows the structure of FIG. 7 after depositing a first maskingmaterial layer over a surface of the substrate and exposing thetriangularly-shaped feature through an opening in the first maskingmaterial layer.

FIG. 9 shows the structure of FIG. 7 after depositing a first tipmaterial in the opening in the first masking material layer.

FIG. 10 shows the structure of FIG. 7 after depositing a second tipmaterial in the opening in the first masking material layer.

FIG. 11 shows the structure of FIG. 7 after planarizing the firstmasking material layer and the second tip material.

FIG. 12( a) shows the structure of FIG. 7 after removing the firstmasking material layer in accordance with one aspect of an embodiment ofthe invention.

FIG. 12( b) shows the tip portion of FIG. 12( a) after affixing thefabricated tip structure to a spring of a separately fabricatedinterconnection element in accordance with one aspect of an embodimentof the invention.

FIG. 13( a) shows the structure of FIG. 7 after depositing anadhesion/seed material over a portion of the planarized surface inaccordance with a second aspect of an embodiment of the invention.

FIG. 13( b) shows the structure of FIG. 7 after patterning a secondmasking material layer over the substrate having an opening aligned tothe tip, the opening extending laterally and/or transversely over thesubstrate from the tip in accordance with a second aspect of anembodiment of the invention.

FIG. 13( c) shows the structure of FIG. 7 after depositing a secondconductive material in the opening of the second masking material layerin accordance with a second aspect of an embodiment of the invention.

FIG. 13( d) shows the structure of FIG. 7 after planarizing the secondmasking material and the second conductive material in accordance with asecond aspect of an embodiment of the invention.

FIG. 14( a) shows the structure of FIG. 7 after removing the maskingmaterial layers to form an interconnection element including a springhaving a single leaf portion and a tip structure in accordance with athird aspect of an embodiment of the invention.

FIG. 14( b) shows the structure of FIG. 14( a) after affixing the tipstructure and spring to a separately fabricated post and spring (in thisexample consisting of one leaf portion) in accordance with a thirdaspect of an embodiment of the invention.

FIG. 14( c) shows the structure of FIG. 14( b) after separating the tipstructure from its substrate to form a free-standing interconnectionelement on a substrate in accordance with a third aspect of anembodiment of the invention.

FIG. 15( a) shows the structure of FIG. 7 after depositing a thirdmasking material layer over a portion of the planarized surface inaccordance with a fourth aspect of an embodiment of the invention.

FIG. 15( b) shows the structure of FIG. 7 after depositing a seedmaterial over a portion of the substrate in accordance with a fourthaspect of an embodiment of the invention.

FIG. 15( c) shows the structure of FIG. 7 after depositing a fourthmasking material layer over a portion of the substrate defining anopening over the second conductive material in accordance with a fourthaspect of an embodiment of the invention.

FIG. 15( d) shows the structure of FIG. 7 after depositing a thirdconductive material in the opening of the fourth masking material layerin accordance with a fourth aspect of an embodiment of the invention.

FIG. 15( e) shows the structure of FIG. 7 after planarizing the thirdmasking material layer and the third conductive material in accordancewith a fourth aspect of an embodiment of the invention.

FIG. 15( f) shows the structure of FIG. 7 after depositing andpatterning additional masking material layers, seed materials, andconductive materials to form two additional leaf portions in accordancewith a fourth aspect of an embodiment of the invention.

FIG. 16( a) shows the structure of FIG. 7 after removing the maskingmaterial layers to form an interconnection element including a springhaving four leaf portions and a tip structure in accordance with a fifthaspect of an embodiment of the invention.

FIG. 16( b) shows the structure of FIG. 16( a) after affixing the tipstructure and spring to a separately fabricated post to form afree-standing interconnection element on a substrate in accordance witha fifth aspect of an embodiment of the invention.

FIG. 17( a) shows the structure of FIG. 7 after depositing a postmasking material layer over the surface of the substrate and forming anopening to the seed material in accordance with a sixth aspect of anembodiment of the invention.

FIG. 17( b) shows the structure of FIG. 7 after depositing a postmaterial in the opening to the seed material in accordance with a sixthaspect of an embodiment of the invention.

FIG. 17( c) shows the structure of FIG. 7 after planarizing the postmasking material layer and the post material in accordance with a sixthaspect of an embodiment of the invention.

FIG. 17( d) shows the structure of FIG. 7 after removing the maskingmaterial layers in accordance with a sixth aspect of an embodiment ofthe invention.

FIG. 17( e) shows the structure of FIG. 7 after affixing theinterconnection element formed in accordance with a sixth aspect of anembodiment of the invention to an electronic component.

FIG. 18 shows a top view illustration of an application for anembodiment of the interconnection element of the invention wherein aplurality of interconnection elements are affixed to an electroniccomponent and contact a plurality of contact pads or terminals arrangedalong the edge of a second electronic component.

FIG. 19 shows a top view illustration of a second application for anembodiment of the interconnection element of the invention wherein aplurality of interconnection elements are affixed on an electroniccomponent and contact a plurality of contact pads or terminals arrangedin a row on a second electronic component.

FIG. 20( a) shows a top view illustration of a first application for anembodiment of the interconnection element of the invention wherein aplurality of interconnection elements are affixed to an electroniccomponent in a diagonal array and contact a plurality of contact pads orterminals on a second electronic component.

FIG. 20( b) shows a top view illustration of a second application for anembodiment of the interconnection element of the invention wherein aplurality of interconnection elements are affixed to an electroniccomponent in a diagonal array and contact a plurality of terminals on asecond electronic component.

FIG. 21( a) shows a top perspective view of a layout of adjacentinterconnection elements fabricated with close spacing tolerances inaccordance with an embodiment of the invention.

FIG. 21( b) shows a cross-sectional view of the layout ofinterconnection elements of FIG. 21( a) in accordance with an embodimentof the invention.

FIG. 21( c) shows a top perspective view of a layout of adjacentinterconnection elements fabricated with close spacing tolerances inaccordance with another embodiment of the invention.

FIG. 21( d) shows a cross-sectional view of the layout ofinterconnection elements of FIG. 21( c) fabricated in accordance with anembodiment of the invention.

FIG. 21( e) shows a top view illustration of a plurality ofinterconnection elements affixed to an electronic component in anoverlayed fashion so that their tips align in accordance with anembodiment of the invention.

FIG. 21( f) shows a top view illustration of a plurality ofinterconnection elements affixed to an electronic component in anoverlayed fashion so that their tips are staggered in accordance with anembodiment of the invention.

FIG. 22( a) shows a top view of a first exemplary layout of a leafportion over a substrate in accordance with the invention.

FIG. 22( b) shows a top view of a second exemplary layout of a leafportion over a substrate in accordance with the invention.

FIG. 22( c) shows a top view of a third exemplary layout of a leafportion over a substrate in accordance with the invention.

FIG. 22( d) shows a top view of a fourth exemplary layout of a leafportion over a substrate in accordance with the invention.

FIG. 22( e) shows a top view of a fifth exemplary layout of a leafportion over a substrate in accordance with the invention.

FIG. 22( f) shows a top view of a sixth exemplary layout of a leafportion over a substrate in accordance with the invention.

FIG. 22( g) shows a top view of a seventh exemplary layout of a leafportion over the substrate in accordance with the invention.

FIG. 23( a) shows a cross-sectional side view of a seventh exemplarylayout of a leaf portion over a substrate in accordance with theinvention.

FIG. 23( b) shows a cross-sectional side view of an eighth exemplarylayout of a leaf portion over a substrate in accordance with theinvention.

FIG. 24( a) shows an embodiment of an interconnection element of theinvention having a plurality of leaf portions of different dimensions.

FIG. 24( b) shows the interconnection element of FIG. 24( a) subjectedto a force at its tip.

FIG. 25( a) shows an embodiment of an interconnection element of theinvention having a plurality of leaf portions coupled to one anotherthrough non-aligned supports.

FIG. 25( b) shows the interconnection element of FIG. 25( a) subjectedto a force at its contact region.

FIG. 26( a) shows an embodiment of an interconnection element of theinvention having a plurality of variable length leaf portions.

FIG. 26( b) shows the interconnection element of FIG. 26( a) subjectedto a force at its contact region.

FIG. 27( a) shows an embodiment of an interconnection element of theinvention having a plurality of leaf portions coupled to one another attheir proximal and distal ends.

FIG. 27( b) shows the interconnection element of FIG. 27( a) subjectedto a force at its contact region.

FIG. 28( a) shows an embodiment of an interconnection element of theinvention having a plurality of leaf portions coupled to another bystaggered supports and a contact region of a tip coupled to a surface ofa superiorly-located leaf portion between its ends.

FIG. 28( b) shows the interconnection element of FIG. 28( a) subjectedto a force at its contact region.

FIG. 29( a) shows a side view of an embodiment of an interconnectionelement of the invention having a plurality of cylindrical leaf portionscoupled to one another by staggered supports.

FIG. 29( b) shows a second side view of the interconnection element ofFIG. 29( a).

FIG. 29( c) shows a top perspective view of the interconnection elementof FIG. 29( a).

FIG. 29( d) shows the interconnection element of FIG. 29( a) subjectedto a force at its contact region.

FIG. 30 shows a top perspective view of an embodiment of a leaf portionof an interconnection element of the invention having a cylindricalshape with a “clover leaf”-shaped opening.

FIG. 31 shows a top perspective view of an embodiment of a leaf portionof an interconnection element of the invention having a “H”-shape.

FIG. 32 shows a top perspective view of an embodiment of a leaf portionof an interconnection element of the invention having a rectangularshape with a rectangularly-shaped opening.

FIG. 33( a) shows a cross-sectional side view of a layout of adjacentinterconnection elements collectively forming an apparatus suitable as amicro-switch.

FIG. 33( b) shows a top perspective view of the layout of FIG. 33( a).

FIG. 33( c) shows a planar top view of the layout of FIG. 33( a).

FIG. 34 shows a second method of fabricating an interconnection elementon a substrate and shows a substrate having a tip structure formedthrough a masking material layer.

FIG. 35 shows the structure of FIG. 34 after removing the maskingmaterial layer that defines the pattern for the tip structure.

FIG. 36 shows the structure of FIG. 34 after introducing a firstconductive material mask layer over the substrate.

FIG. 37 shows the structure of FIG. 34 after planarizing the firstconductive material mask layer and the tip structure.

FIG. 38 shows the structure of FIG. 34 after patterning a second maskingmaterial layer and introducing a first body material.

FIG. 39 shows the structure of FIG. 34 after removing the second maskingmaterial layer.

FIG. 40 shows the structure of FIG. 34 after introducing a secondconductive material layer mask over the structure.

FIG. 41 shows the structure of FIG. 34 after planarizing the secondconductive material layer mask and the first body material.

FIG. 42 shows the structure of FIG. 34 after introducing a thirdconductive material layer mask over the structure.

FIG. 43 shows the structure of FIG. 34 after patterning a third maskingmaterial layer over the structure.

FIG. 44 shows the structure of FIG. 34 after exposing the first bodymaterial through the patterning of second masking material layer.

FIG. 45 shows the structure of FIG. 34 after patterning a second maskingmaterial layer to define an opening for a second body material.

FIG. 46 shows the structure of FIG. 34 after introducing a second bodymaterial.

FIG. 47 shows the structure of FIG. 34 after removing the second maskingmaterial layer.

FIG. 48 shows the structure of FIG. 34 after introducing a fourthconductive material layer mask over the structure.

FIG. 49 shows the structure of FIG. 34 after planarizing the fourthconductive material layer mask and the second body material.

FIG. 50 shows the structure of FIG. 34 after forming a plurality of bodymaterial layers and a post structure.

FIG. 51 shows the structure of FIG. 34 after removing a plurality ofconductive material layer masks.

FIG. 52 shows the structure of FIG. 34 after removing a seed layer toexpose an underlying release layer of the substrate.

DETAILED DESCRIPTION OF THE INVENTION

The invention relates to interconnection elements, including contactelements. According to one aspect of the invention, the inventioncontemplates a method of forming an interconnection element having abody including a plurality of resilient or flexural elements, e.g., leafportions. The invention also relates to a method of bringing togethertwo substrates, such as an electronic component having a plurality ofinterconnection elements with a second electronic component having anarray of contact pads or terminals.

Suitable electronic components include, but are not limited to, anactive semiconductor device, a memory chip, a portion of a semiconductorwafer, a ceramic substrate, an organic substrate, a PCB, an organicmembrane, a polyimide sheet, a space transformer, a probe card, a chipcarrier, and a socket. The electronic component may be an active deviceor a passive device that supports one or more electronic connections. Ingeneral, suitable electronic components include, but are not limited to,devices comprising an integrated circuit having at least two contacts orterminals providing electrical access to the circuit. Such a device isrepresentatively demonstrated by an integrated circuit chip (ormicrochip) having a plurality of exposed contacts or terminals providingaccess to the integrated circuit of the device.

The interconnection element or elements of the invention may befabricated on or independent of the electronic component to which it isor they are joined. In the case of independent fabrication, theinvention contemplates that the interconnection element or elements canbe fabricated with a shape, size, and metallurgy that are not limited bythe materials and layout considerations associated with the manufactureof the electronic component. Independent fabrication also avoids theexposure of the electronic component to the process conditionsassociated with forming the interconnection element.

Disposed on an electronic component such as a space transformer of aprobe card assembly, the interconnection elements of the invention aredesigned to accommodate contact pads or terminals of electroniccomponents having very small pitch or spacing tolerances. In oneembodiment, the interconnection elements adopt alternating orientation(e.g., left-right-left-right) so as to achieve a greater pitch betweentheir post portion than at the tip portion. In another embodiment, theinterconnection elements adopt alternating lengths (e.g.,short-long-short-long) so as to achieve a greater pitch between the postportion than at the tip portion of adjacent interconnection elements.Similarly, alternating interconnection elements can be fabricated tohave a greater pitch at their tip portions than their post portions. Insummary, the interconnection elements, whether fabricated on orindependent of the electronic component to which they are joined mayadopt a variety of orientations to accommodate various configurationsassociated with the electronic components which they connect.

FIG. 1 and FIG. 2 illustrate one embodiment of a spring interconnectionelement. Methods of formation of such a spring interconnection elementare described in detail in application Ser. No. 09/205,023 entitled“Lithographic Contact Elements.” FIG. 1 shows interconnection element 10comprising post 13, beam or body 14, and tip structure 16. Post 13 isdisposed on terminal 11 of electronic component 9. Post 13 has a height,h₂. Body 14 is coupled at one end to post 13. For consistency, in thediscussion that follows the end of an elongate beam body that is coupledto the post will be referred to as the proximal end. Of course, one ofskill in the art will recognize that when discussing a body structurethat is a beam or a plurality of beams or leaf portions, elements neednot be positioned at ends of the beam.

In one embodiment shown in FIG. 1, body 14 is a single beam having athickness equivalent to a height, t₁, and length, l_(B). At the otherend of body 14 (e.g., the distal end) and coupled to a side oppositepost 13 is contact or tip structure 16. Tip structure 16 has a height,h₁, from the surface of body 14.

FIG. 2 shows interconnection element 10 under load such as whenaccommodating a substrate under test. In this case, substrate 20 havingterminal 21 is brought into contact with interconnection element 10 andan inferiorly-directed (e.g., downward) force, F, is applied at tipstructure 16 of interconnection element 10 to deflect interconnectionelement 10 at its distal end towards electronic component 9. FIG. 2shows deflected interconnection element 10 separated from electroniccomponent 9 at its distal end by a height, h₃.

Under load, such as when contacting substrate 20, body 14 ofinterconnection element 10 deflects by an amount represented in FIG. 2by δ. A spring constant, k, may be calculated for this deflection asfollows:

k=F/δ.

Controlling the spring constant for each interconnection element of anelectronic component, such as in a probe card assembly, allows aconsistent contact force to be applied to each terminal, such asterminal 21 of a substrate under test (such as substrate 20). Hundredsto thousands of interconnection elements may be utilized in a probingoperation and many tens of thousands in a wafer-scale contactor. Thus,consistent spring force is particularly significant.

Decreasing device sizes allows a corresponding increase in contact orterminal density. In order for interconnection elements on a secondelectronic component to accommodate the increased array density by acorresponding interconnection element array on the second electroniccomponent, the interconnection element array must correspondingly becomemore dense. One way to increase the density of an interconnectionelement array on an electronic component is to reduce the size of theindividual interconnection elements. Thus, an interconnection element,such as interconnection element 10 of FIG. 1, may be reduced in itslength, l_(B), and its width (not shown) to permit a greater density(e.g., smaller pitch) array on an electronic component (e.g., increasethe number of interconnection elements that occupy a given space).

Reduction in the length and width of a particular interconnectionelement (e.g., reduction in the surface area of the interconnectionelement) affects the mechanical properties of the interconnectionelement. For example, the spring constant of a resilient interconnectionelement, k, is directly related to the geometry (e.g., length, width,and thickness) of the interconnection element. Thus, reduction inthickness for a given length and width beam, correspondingly reduces thespring constant of the interconnection element (k ∝thickness³). Areduction of the spring constant generally reduces the amount of load orforce that may be applied to interconnection elements for a givendeflection. Similarly, a reduction in the width of an interconnectionelement for a given length and thickness, correspondingly reduces thespring constant of the interconnection element (k ∝width), as does areduction in length for a given width and thickness (k ∝length⁻³).

In certain situations, it may be desirous to reduce the size of aninterconnection element without reducing the amount of load or forcedesired to be applied to the interconnection element. In order toaccommodate an acceptable force, for example, on an interconnectionelement having a substantially rectangular beam in a high densityinterconnection element array, the thickness of the body of aninterconnection element may be increased. In FIG. 1, for example, thethickness of body 14, t₁, may be increased to account for a decreasedlength, l_(B), and width. However, increasing the thickness of the bodygenerally increases the stress of the body. Increasing the stress of abody decreases the longevity or number of compression cycles to failureof the interconnection element.

The stress of a particular body material is generally a measurement ofthe deformation of the material under a force or load. In general, amaterial may withstand a certain amount of stress in which thedeformation is reversible. Beyond this point, the deformationreversibility decreases to a point of “permanent set” corresponding tothe yield stress of the material. The yield stress is materialdependent. In general, in spring applications such as representativelydescribed for the interconnection element of the invention, the maximumstress on an interconnection element material is designed to be lessthan about one-half the 0.2 percent offset yield stress of the materialfor maximum longevity of operation.

The interconnection element of the invention addresses an objective ofincreasing the density of interconnection elements on an electroniccomponent by adjusting the thickness of each interconnection element,assuming that the length and width are set to a predetermined maximumpermitted by the geometry. In this manner, an increase in the density ofinterconnection elements on an electronic component may be achievedwithout a corresponding reduction in spring constant or a reduction inthe acceptable load or force applied to the interconnection elements.The increased thickness of the portion of the interconnection element ofthe invention may also be achieved without a reduction in the allowablemaximum stress on the material.

FIG. 3 and FIG. 4 illustrate one embodiment of an interconnectionelement of the invention. FIG. 3 shows interconnection element 30comprising post 33, body 34, and contact or tip structure 36. Post 33 isdisposed as a first attachment element on terminal 11 of electroniccomponent 9. Post 33 has a height, h₂, over substrate 9. Body 34 iscoupled at one end of post 33. Body 34 includes a plurality (in thiscase, four) flexural elements or leaf portions 35 each having athickness or height, t₂, that collectively define a width (not shown), athickness or height, t₃ and length, l_(B). The superiorly-located leafportion 35 defines a superior surface for body 34 to which tip structure36, as a second attachment element, is coupled. Tip structure 36 has aheight, h₁, from the superior surface of spring 34. In this embodiment,tip structure 36 is coupled to body 14 at an end opposite post 13.Again, it is to be appreciated that this configuration is onlyillustrative.

FIG. 4 shows interconnection element 30 under load such as whenaccommodating a substrate under test. In this case, substrate 20 havingterminal 21 is brought into contact with interconnection element 30through an inferiorly-directed force, F, applied at tip structure 36 ofinterconnection element 30 to deflect interconnection element 30. Thedeflection, δ₂, of interconnection element 30 causes tip structure 36 to“wipe” contact pad or terminal 21 in a lateral direction as theinterconnection element deflects. This wiping action serves, in onesense, to improve the connection between tip structure 36 and contactpad or terminal 21 by cutting through debris or build-up on the contactor terminal.

In one embodiment, the height of the post, h₂, is greater than theheight of the tip structure, h₁, so that post 33 determines theover-travel or deflection distance of body 34. A suitable over-travel ordeflection distance according to current technologies is 2-8 mils(50-200 microns). As shown in FIG. 4, electronic component 20“bottoms-out” on the superior surface of body 34. In this configuration,the superior surface of body 34 may be coated with an insulative layerto limit possible errant currents.

Other alternatives for limiting the over-travel or deflection distanceof the interconnection element of the invention are also suitable. Forexample, the height of tip structure, h₁, can be greater than the heightof the post, h₂. In this situation, electronic component 20 will notbottom-out on the superior surface of body 34. To protect the distal endof the inferiorly-located leaf portion of body 34 from contacting thesurface of electronic component 9, travel stop 37 (indicated in dottedlines) may be added. Alternatively, post stop 38 (also indicated indotted lines) may be fabricated to a predetermined height adjacentinterconnection element 30 to limit the superiorly-directed advancementof electronic component 20. Alternative travel stop 37 and post stop 38,respectively, are, in one aspect, comprised of an insulating material.

FIG. 5 and FIG. 6 graphically compare the force and stress of a singlebeam body and a leaf portion body interconnection element according tothe invention. FIG. 5 shows that the amount of force to deflect a bodyis greater for a single beam structure having a thickness t₁ such asshown in FIG. 1 as compared to a single leaf portion having a thicknesst₂ shown, for example, in FIG. 3 provided the thicknesses are set asshown.

FIG. 6 shows a graphical representation of the stress of a material fora single beam body and a leaf portion of, for example, a multiple-leafbody of an interconnection element according to the invention. FIG. 6shows that for a given deflection distance, corresponding, for example,to a contact force shown in FIG. 5, the stress on a body material, σ, isgreater for a single beam of thickness, t₁, than a leaf portion ofthickness, t₂, of a multiple-leaf body. In order to remain below themaximum stress, σ_(max), the deflection distance of the single beam bodymust be limited. Increasing the thickness of the single beam furtherlimits the deflection distance even more.

In general, in the example of an interconnection element having arectangular body or spring such as shown in FIG. 1 (single beam) andFIG. 3 (multiple leaf), the spring constant of an interconnectionelement is directly related to the thickness of the interconnectionelement. Thus, reducing the thickness of a body portion of aninterconnection element reduces the spring constant (k_(leaf)<k_(beam))which correspondingly reduces the contact force required to deflect theinterconnection element a predetermined distance. In order to achieve adesired spring constant of, for example, the spring constant of thebeam, k_(beam), multiple (n) leaf portions each having a thickness, t₂,are combined such that n·k_(leaf)≈k_(beam). It is to be appreciated thatthe spring constant of an interconnection element, including a multipleleaf interconnection element described in the invention will vary withthe application (e.g., the length of the beam spring, interconnectionmaterial, the desired deflection distance, etc.).

As shown in FIG. 6, the stress on a single leaf portion of, for example,a multiple-leaf body (the multiple-leaf body collectively having asimilar material thickness to a single beam) is much less for a givendeflection distance (e.g., a given amount of force) as compared to thesingle beam body. Accordingly, a single leaf portion may have a muchgreater compliance and be subjected to a much greater deflection than asingle beam body of equivalent spring constant and remain below themaximum stress of the material. Thus, in designing an interconnectionelement according to the invention, the thickness of each leaf portion,t₂ (see FIG. 3) may be determined to be below the maximum stress and thenumber of leaf portions may be selected to achieve a desired springconstant.

The following example compares a single beam body (spring)interconnection element such as interconnection element 10 with aleaf-portioned body (spring) interconnection element such asinterconnection element 30. In this example, each interconnectionelement is limited to a body length, l_(B), of 10 mils (250 μm) and amaximum stress, σ_(MAX), of 1×10⁵ pounds per square inch (psi) or 7000kilograms-force per square centimeter (kg/cm²). The body of eachinterconnection element is comprised of a nickel-cobalt (NiCo) alloywith a Young's modulus of 30×10⁶ psi (2.1×10⁶ kg/cm²).

In the case of a single beam body having a thickness, t₁, of 0.001inches (25.4 μm) and a constant width of 0.0055 inches (139.7 μm), themaximum spring deflection is 2.2×10⁻⁴ inches (5.6 μm) and the force is4.1 gram-force (gmf). The spring constant is 18.7 gmf/mil (0.74 gmf/μm).

In the case of a two-leaf structure with equivalent spring rate, thespring constant for each leaf portion (k_(1/2)) is approximately 9.3gmf/mil (0.36 gmf/μm) for a thickness, t₂, of 0.00079 inches (2.0 μm).Such a configuration allows a deflection distance of 2.8×10⁻⁴ inches(7.1 μm) to develop 100 ksi stress. By combining two leaf portions, aspring constant of 18.6 gmf/mil (0.73 gmf/μm) is produced, approximatelythe spring constant of the single beam described above. The multi-leafbody, however, is capable of a deflection of 2.8×10⁻⁴ inches (7.1 μm) ascompared to 2.2×10⁻⁴ inches (5.6 μm) for the single beam body, animprovement of 127 percent in allowed deflection. For a threeleaf-portioned body, the improvement in allowed deflection is 145percent; for a four leaf-portioned body, 162 percent.

It is to be appreciated that the above example representatively comparesa single beam interconnection element with a multiple leaf portioninterconnection element. Accordingly, the dimensions of theinterconnection element bodies and values of spring constant anddeflection distance are similarly representative and not intended toconfine the invention. For example, multiple leaf structures havingindividual spring constants on the order of 0.05 to 0.3 gmf/mil (0.002to 0.02 gmf/μm) or greater are useful in interconnection elementsemploying multiple leaf portions (e.g., two or more) according tocurrent state of the art applications.

As contact pad or terminal densities on electronic components increase,the area of corresponding interconnection elements of a correspondingelectronic component configured to connect to or probe the contact padsor terminals will be reduced. Thus, for example, the length and width ofindividual interconnection elements on an electronic component will bedetermined by the array of the corresponding contact pad or terminalarray of the electronic component to be contacted. The invention offersthe ability to achieve a desired spring constant, contact force, anddeflection distance and meet the increased contact pad or terminaldensity requirements of current and future technologies.

A. Fabrication of a Multi-Leaf or Multi-Tier Spring Interconnect Element

FIGS. 7-17( e) illustrate one method of making an interconnectionelement in accordance with one embodiment of the invention. In oneaspect, an interconnection element that is a cantilever including apost, a body comprising a plurality of leaf portions, and a tipstructure will be fabricated in this embodiment. It is to be appreciatedthat at a given time, a number of interconnection elements can be formedon a substrate. The method described below focuses on the formation of asingle interconnection element. The discussion, however, applies also tothe fabrication of a number of interconnection elements on a substrate,such as a sacrificial substrate or an electronic component, at a giventime. Typically, each of the interconnection elements fabricated on asubstrate will have substantially similar characteristics (e.g.,dimensions, shape, etc.). It is also appreciated, however, that thecharacteristics of the interconnection elements of a substrate can beindividually controlled and determined for given applicationrequirements.

FIG. 7 shows structure 100 including substrate 110 that is a sacrificialsubstrate such as, for example, a semiconductor (e.g., silicon)substrate. For illustration purposes, substrate 110 is oriented to showa finished interconnection element. The orientation during manufacturingmay be quite different. The method of making an interconnection elementwill be described according to current processing methodologiesincluding device scale. It is to be appreciated that the principles ofthe invention may be adapted to future methodologies and that thetechniques described are scalable.

Formed in a surface of substrate 110 is a pyramidally-shaped feature.Methods for forming a pyramidally-shaped feature are described in detailin commonly-owned pending PCT Application No. PCT/US97/08606, publishedNov. 20, 1997 as WO97/43653. In PCT Application No. PCT/US97/08606, amethod is described whereby a pyramidally-shaped feature is formed bythe patterning of a masking material having a preferably square openingmeasuring, according to current technologies, approximately 1-4 mils(25-100 μm) on a side over a semiconductor substrate. Next, thesubstrate is etched to form the pyramidally-shaped depression. In thecase of certain silicon semiconductor substrates, silicon will tend tobe self-limiting as the etching proceeds along the crystal plane, suchas at approximately 54.74° for silicon. In other words, the depressionwill extend to a depth that is dictated by the size of the mask openingand the nature of the substrate. For example, with square openings of2.5 mils (63.5 μm) per side, the depth of the depression will beapproximately 2 mils (50.8 μm) in wafer-grade silicon.

Other methods of forming pyramidally-shaped features are described incommonly-owned U.S. Pat. No. 5,809,128 and co-pending and commonly-ownedU.S. patent application Ser. No. 08/802,054, titled “MicroelectronicContact Structure, and Method of Making Same.”

Overlying the surface of substrate 110 is release layer 125. Releaselayer 125 is, for example, a metal such as aluminum ortitanium-tungsten, deposited to a thickness of approximately 5000angstroms (Å) using conventional deposition techniques. Overlyingrelease layer 125 on the surface of substrate 110 is seed layer 130.Seed layer 130 is, for example, copper, palladium, or titanium-tungstenthat facilitates a further deposition technique such as anelectroplating process such as by establishing an appropriate potentialfor an electrolytic process. In one embodiment, seed layer 130 oftitanium-tungsten is introduced over the surface of substrate 110 to athickness of approximately 5000 Å using conventional (e.g., sputter)deposition techniques. Alternatively, a bilayer of two materials may beintroduced as seed layer 130. In one embodiment, a layer of gold orpalladium is introduced at a thickness of, for example, a few thousandangstroms followed by the introduction of a second material such astitanium-tungsten. Seed layer 130 may be introduced as a blanket layerover substrate 110 or as multiple, non-contiguous regions.

FIG. 8 shows structure 100 after the introduction and patterning offirst masking material layer 135 over substrate 110. First maskingmaterial layer 135 is, for example, a photopolymer (e.g., a positive ornegative photoresist) that is spin-coated onto the surface of substrate110 to a thickness of the desired height of a tip structure of aninterconnection element taking into consideration the possibility ofplanarizing a portion of first masking material layer 135 with tipstructure material. Approximately 1-4 mils (25-100 μm) is a usefulheight range for many applications. First masking material layer 135 ispatterned to have an opening over feature 120.

Next, as shown in FIG. 9, first tip material 137 is introduced in theopening in first masking material layer 135. Suitable materials forfirst tip material 137 include, but are not limited to, palladium (Pd),gold (Au), and rhodium (Rh) and their alloys, including nickel (Ni) andcobalt (Co) alloys. First tip material 137 is introduced, in oneexample, to a thickness of about 1 to 5 μm but more can be used—eventens of microns or more. Suitable introduction techniques include, butare not limited to, electroplating, chemical vapor deposition, sputterdeposition, and electroless plating. In this example, first tip material137 serves as an outer contact layer in the finished product.

FIG. 10 shows a process of forming an interconnection element accordingto an embodiment of the invention where second tip material 140 isintroduced to a suitable thickness. This may be at least the height offirst masking material layer 135 (the height of opening 120) or greaterthan such height. Suitable introduction techniques include, but are notlimited to, electroplating, chemical vapor deposition, sputterdeposition, and electroless plating. In one embodiment, second tipmaterial 140 is an alloy of nickel and cobalt (NiCo) introduced by anelectroplating process to a height greater than the height of firstmasking material layer 135 (i.e., overplating). A suitable total heightis about 1-4 mils (25.4-101.6 μm), particularly about 3 mils (76.2 μm).

FIG. 11 shows structure 100 after planarizing second tip material 140and first masking layer 135 in accordance with an embodiment of theinvention. The planarization is accomplished, for example, by amechanical polish or a chemical-mechanical polish with a suitableslurry. Suitable mechanical polishes include diamond-based materials andsilicon carbide. Suitable slurries for a chemical-mechanical polish ofthe materials described above include silicon dioxide, aluminum oxide,and cesium oxide in a pH-adjusted slurry. The planarization described inFIG. 11 defines the height of the tip structure of an interconnectionelement.

In a first aspect of an embodiment of the invention, the tip structureof first tip material 137 and second tip material 140 may be removed andseparately affixed to an interconnection element, such as for example,an interconnection element containing a post and a body formed on anelectronic component. FIG. 12( a) shows structure 100 after removingfirst masking material layer 135. In the example where first maskingmaterial layer 135 is a photoresist, first masking material layer 135may be removed by an etch (e.g., oxygen ashing), reactive ion etching,laser ablation, or wet etching. The removal of first masking materiallayer 135 may also remove seed layer 130. Alternatively, an additionalprocedure (e.g., etch) may be performed to remove seed layer 130 andexpose release layer 125. Once first masking material layer 135 and seedlayer 140 are removed, the tip structure of first tip material 137 andsecond tip material 140 may be separated from substrate 110 at releaselayer 125. In the example where release layer 125 is aluminum, the tipstructure may be removed from substrate 110 by dissolving release layer125 using a sodium hydroxide (NaOH) solution as known in the art. Othermethods of separation including but not limited to chemical etching andheat are also suitable, as known in the art. In the example where seedlayer 130 is a bilayer of gold followed by titanium-tungsten, a portionof seed layer 130 that may remain on the tip structure may serve asappropriate contact material.

Before the tip structure is separated from substrate 110, the tipstructure may be combined with a post and a body as shown in FIG. 12( b)by, for example, brazing, soldering, or welding. FIG. 12( b) shows anexample of interconnection element 1500 coupled to electronic component1000. Interconnection element 1500 includes post 1650, coupled toterminal 1010 of electronic component 1000 and body 1550. Body 1550includes multiple (e.g., four shown) cantilever leaf portions. A methodof forming the leaf portions of a body will be discussed below withrespect to a further aspect of an embodiment of the invention. Forpresent purposes, FIG. 12( b) shows the tip structure of first tipmaterial 137 and second tip material 140 secured to a superior surfaceof body 1550 at an end opposite post 1650 in this example.

FIG. 13( a) shows a second aspect of an embodiment of the invention.Starting from structure 100 as shown in FIG. 11, FIG. 13( a) showsstructure 100 after rendering a portion of first masking material layer135 conductive to define an electrode area for a body of theinterconnection element that is to be formed by an electroplatingprocess. In one embodiment, a portion of an area over first maskingmaterial layer 135 is covered with a thin adhesion/seed layer. Typicaladhesion materials include, but are not limited to, titanium, tungsten,molybdenum, chrome, and copper, alone or as an alloy. Typical seedmaterials include, but are not limited to, gold, copper, silver,platinum and palladium. Another example of an adhesion/seed layer is anadhesion layer of palladium-tin chloride and a seed layer of electrolesspalladium. Seed layer 145 may be introduced via a blanket deposition,such as a sputter deposition. For an electroplated nickel-cobalt layer,for example, a seed layer having a thickness according to currenttechnologies of about between 1500 to 6000 Å, may be suitably introducedby, for example, a blanket sputter deposition process over the surfaceof first masking material 135. Alternatively, seed layer 145 may beintroduced as a plurality of “traces,” each trace corresponding to anarea over a first masking material layer 135 where the body of theinterconnection element is to be formed to serve, in one manner, as anelectroform whereupon the body can be fabricated.

In yet another embodiment, a stencil (shadow mask) may be introducedover the surface of first masking material layer 135. A stencil may beused, for example, to introduce a discontinuous adhesion/seed layer. Thestencil typically will have a plurality of openings extending laterallyfrom an area above the corresponding tip structure (indicated by firsttip material 137 and second tip material 140) to define areas for thebody of the interconnection elements. The stencil may suitably be a thin(e.g., about 2 mils (50.8 μm) thick for current technologies) foil ofstainless steel, tungsten, or molybdenum that may be punched or etchedto have openings. The stencil can be any suitable material having anysuitable thickness that will permit seed layer 145 to be deposited ontofirst masking material layer 135 in a pattern of conductive tracescorresponding to the shape of the opening in the stencil. With thestencil in place (typically, slightly above the surface of substrate110), seed layer 145 is deposited, such as by sputtering, onto theexposed surface of first masking layer 135. The stencil may then beremoved.

Consideration should be given, in certain instances, to the selection ofthe material for the masking material layer and the process fordeposition of the seed layer. In general, the masking material should bestable in the environment of the deposition method. Compatibilityconsiderations are within the level of ordinary skill in the art.

Next, as shown in FIG. 13( b), an area over substrate 110 is covered bysecond masking material layer 150, again such as a photopolymer (e.g.,photoresist) bearing in mind the consideration of using multiple maskingmaterials in the presence of conductive layers, including seed layers.Second masking material layer 150 is patterned to define opening 151over structure 100.

Second masking material layer 150 defines an area over structure 100 fora first leaf portion (e.g., a cantilever leaf portion) of a body inaccordance with one embodiment of the invention. The area correspondingto opening 151 in second masking material layer 150 will be determined,in this embodiment, based, in part, on the desired area for the leaf.The desired area of opening 151 will depend, to a large extent in oneembodiment, on the density and disposition (distribution) of a contactpad or terminal array that an electronic component of a plurality ofinterconnection elements will be probing or contacting. For example, foran electronic component having a pitch of approximately 6 mils (152 μm)or less between contacts or terminals, the length and width of aninterconnection element in an array must be sized so that it can contactone contact pad or terminal and allow, for example, an adjacentinterconnection element of the array to contact an adjacent contact pador terminal. One way this is achieved is shown by the illustration shownin FIG. 20( a) and FIG. 20( b). In FIG. 20( a), for example, contacts orterminals 710 are disposed on an electronic component having a pitch of,for example, 6 mils (152 μm). Interconnection elements 715 are disposeddiagonally on electronic component 720 (shown in dashed lines).Interconnection elements 725 are cantilever interconnection elementshaving a rectangular body of a plurality of leaf portions (not shown inFIG. 20( a)). Each interconnection element has a length of approximately12 mils (304.8 μm) and a width of 3 mils (76.2 μm) or a total area of 24mil² (2.3×10⁴ μm²). Such an area will correspond, in one embodiment, tothe area of each leaf portion of a cantilever spring of aninterconnection element such as illustrated in the process of FIGS.7-17( e).

The thickness of second masking material layer 150 will determine inpart the thickness of a leaf portion of the body of the interconnectionelement formed by the process in this embodiment. Thus, second maskingmaterial layer 150 is introduced to a desired thickness of a leafportion of a body of the interconnection element bearing in mind asubsequent planarization step. A suitable thickness of a leaf portionwill be determined based in part on considerations of the desired springconstant, the deflection distance of the body, and the stress propertyof the material chosen for the leaf portion of a body. In oneembodiment, for a nickel-cobalt body (having a Young's modulus of 30×10⁶psi (2.1×10⁶ kg/cm²) and maximum stress, σ_(m) of 1×10⁵ psi (7000kg/cm²), a leaf portion having a length of 21 mils (533 μm) and athickness of about 0.5 mil (12.7 μm) will support about 1 mil (25.4 μm)of compliance.

FIG. 13( c) shows structure 100 after introducing first body material155 over the surface of substrate 110. In one embodiment, first bodymaterial 155 is conductive material introduced by an electroplatingprocess with an electroplate alloy such as nickel-cobalt. In FIG. 13(c), first body material 155 is introduced to a thickness greater thanthe thickness of second masking material layer 150. As noted, it is tobe appreciated that the amount introduced and the thickness of firstbody material 155 will depend, in part, on the desired thickness of theparticular leaf portion of the body.

As shown in FIG. 13( d), after the introduction of first body material155 over substrate 110, first body material 155 and second maskingmaterial 150 are planarized by way of, for example, a grinding processor a chemical-mechanical polish such as described above to form a leafportion of the interconnection element on substrate 110. Planarizationof first body material 155 and second masking material 150 controls thefinal thickness of the leaf portion of the body (i.e., controls thethickness of first body material 155) thus allowing a determinable andconsistent leaf portion to be fabricated.

In a third aspect of an embodiment of the invention, the tip structureof first tip material 137 and second tip material 140 and a leaf portionof first body material 155 may be removed and separately affixed to aninterconnection element, such as for example, an interconnection elementcontaining a post and, optionally, a body of one or more leaf portionsformed on an electronic component. FIG. 14( a) shows structure 100 afterthe further processing step of removing first masking material layer 135and second masking material layer 150. In the example where firstmasking material layer 135 and second masking material layer 150 is aphotoresist, the layers may be removed by an etch (e.g., oxygen ashing),reactive ion etching, laser ablation, or wet etching. Once the maskingmaterial layers are removed, the tip structure and leaf portion body maybe removed from substrate 110 by, for example, dissolving release layer125 using a sodium hydroxide (NaOH) solution as known in the art.

Before the tip structure and leaf portion body are separated fromsubstrate 110, the leaf portion may be combined with a post and,optionally, one or more leaf portions as shown in FIG. 14( b) by, forexample, brazing, soldering, or welding. FIG. 14( b) shows an example ofinterconnection element 1550 coupled to electronic component 1580.Interconnection element 1550 includes post 1572 and leaf portion 1575.The affixing of the leaf portion of first body material 155 to leafportion 1575 provides a spacer between the leaf portions. The amount ofconnecting material can be varied to adjust this spacing. FIG. 14( c)shows a free-standing interconnection element after the separation ofsubstrate 110 from the tip structure.

FIG. 15( a) shows a fourth aspect of an embodiment of the invention.Starting from structure 100 as shown in FIG. 13( d), FIG. 15( a) showsdepositing of third masking material layer 158 over a surface ofstructure 100. In this embodiment, third masking material layer 158 is,for example, a photoresist similar to the previous masking materiallayers. Third masking material layer 158 may also be a metal layer(e.g., copper), conductive polymer, or other layer preferred for laterremoval by etching (wet or dry) or solvent removal. The thickness ofthird masking material layer 158 defines, in part, the thickness of agap between adjacent leaf portions of a spring of the interconnectionelement. Third masking material layer 158 also defines a portion offirst body material 155 to which a subsequent leaf portion of a body ofthe interconnection element may be coupled. Stated alternatively, thirdmasking material layer 158 serves, in this embodiment, to provide anarea less than the entire surface area of first body material 155 toconnect a second leaf portion and inhibit the plating together ofadjacent leaf portions. Opening 159 provides access to first bodymaterial 155 to allow plating to a portion of first body material 155.

In one embodiment, third masking material layer 158 is a layer ofphotoresist similar to the previous masking material layers. Thirdmasking material layer 158 may be, for example, on the order of 0.1 to 5μm.

In the discussion that follows, the masking material layers, includingthird masking material layer 158 will be removed leaving a free standinginverted interconnection element on substrate 110 and an air gap betweenadjacent leaf portions of the body of the interconnection element. As analternative to introducing a removable masking material layer to beremoved to form an air gap between adjacent leaf portions, a thin layerof an “interleaf” material may be introduced that inhibits the completeplating of adjacent leaf portions and will not inhibit the deflection ofindividual leaf portions. Suitable interleaf material includes, but isnot limited to, TEFLON® polymers (commercially available from E.I.duPont de Nemours & Co. of Wilmington, Del.) diamond, brass, or aPARALENE® polymer (commercially available from E.I. duPont de Nemours).Opening 159 is patterned with the interleaf material to first bodymaterial 155 to allow plating of a subsequent leaf portion to the leafportion that is first body material 155.

FIG. 15( b) shows the introduction of another adhesion/seed layer.Adhesion/seed layer 160 may be, in one embodiment, similar toadhesion/seed layer 145 and may be introduced via a blanket deposition.For an electroplated nickel-cobalt, for example, an adhesion/seed layerof gold or copper having a thickness of 3000-5000 Å may be suitablyintroduced over the surface of third masking material layer 158.

As shown in FIG. 15( c), an area of structure 100 is covered with fourthmasking material layer 161, again such as a photoresist similar to theprevious masking material layers bearing in mind considerations of usingmultiple masking material layers in the presence of conductive layers.Fourth masking material layer 161 is patterned to define opening 162that defines an area for a second leaf portion of the body of theinterconnection element. In one embodiment, the patterning of fourthmasking material layer 161 defines an area (e.g., a length and width fora cantilever leaf portion) similar to second masking material layer 150.The considerations of the thickness of fourth masking material layer 161are similar to the considerations discussed above with reference tosecond masking material layer 150. In other embodiments, leaf portionsof a spring may have different areas. Leaf portions may be dissimilarnot only in length (as illustrated in FIGS. 24( a) and 24(b)), but evenprofile. The configuration of the individual leaf portions can beselected by the designer for optimal performance in a particularenvironment. The invention provides a mechanism for individuallyconfiguring leaf portions to suit a designer's needs.

Next, as shown in FIG. 15( d), second body material 163 is introducedover substrate 110. In one embodiment, second body material is aconductive material introduced through an electroplating process with anelectroplated alloy such as nickel-cobalt. Second body material 163 isintroduced to a thickness greater than the thickness of fourth maskingmaterial layer 161 of a second leaf portion of the body of theinterconnection element.

As shown in FIG. 15( e), after the introduction of second body material163 over substrate 110, second body material 163 and fourth maskingmaterial layer 161 are planarized by way of, for example, a grindingprocess or a chemical-mechanical polish to form a second leaf portion ofa body of the interconnection element. As noted above, in the case of acantilever leaf portion of a body, the thickness will depend to a largeextent on the desired spring constant, the deflection distance, and thematerial stress. In one embodiment, the thickness of second bodymaterial 163 will be similar to the thickness of first body material155. In other embodiments, such as those illustrated below, leafportions of a body may have different thicknesses and different profilesto modify the properties of the interconnection element.

The above-described process and patterning of masking material layers,introducing a seed layer, introducing a conductive material, andplanarizing a masking material layer and the body material may berepeated numerous times to form additional leaf portions of a body of aninterconnection element. The number of leaf portions will depend,primarily, on the desired spring constant for a predetermined deflectiondistance and material stress for the material of the interconnectionelement of the invention. FIG. 15( f) shows structure 100 after thesubsequent introduction, patterning, and planarizing steps of formingtwo additional leaf portions of a body of the interconnection element.In total, an interconnection element shown in FIG. 15( f) has a body offour leaf portions.

FIG. 16( a) and FIG. 16( b) show a fifth aspect of one embodiment of theinvention. In this aspect, the fabrication of the component for theinterconnection element formed by the lithographic techniques describedis substantially complete with the formation of a spring interconnectionelement having a tip structure of first tip portion 137 and second tipportion 140 and a body of multiple (e.g., four) leaf portions denotedprincipally by body material 155, 163, 166, and 170. FIG. 16( a) showsstructure 100 after removing the masking material layers (e.g., maskingmaterial layers 135, 150, 158, 161, 164, 167, 168, and 169). In theexample where each of the masking material layers are a photoresist, thestep of removing the masking material layers may be accomplished with anetch (e.g., oxygen ashing), reactive ion etching, laser ablation, or wetetching. An additional etch may be required to remove excess orundesired portions of the various seed layers. However, because the seedlayers are typically thin (e.g., about 5000 Å according to currenttechnologies), any excess or undesired seed layer material is typicallyremoved with the removal of the masking material layer(s). In thismanner, FIG. 16( a) shows an interconnection element affixed at its tipto substrate 110 and a body of four laterally and/or transverselyextending leaf portions.

The sacrificial substrate of FIG. 16( a) including a tip structure andbody of an interconnection element may be affixed to aseparately-fabricated post to form an interconnection element on anelectronic component as shown in FIG. 16( b). In this manner,sacrificial substrate 110 is aligned with post 1650 so that theinferiorly located leaf portion of the body (relative to the tipstructure) may be affixed to post portion 1650 at a proximal end of theleaf portion (an end opposite the tip structure end of the leaf portion)to create a cantilever body as shown in FIG. 16( b). The body may beaffixed to post 1650 by, for example, soldering, welding, or brazing.Separately fabricated post 1650 is coupled to electronic component 1010at a contact pad or terminal of electronic component 1010. Post 1650 maybe formed directly on an electronic component or transferred from asacrificial substrate.

Once the body of the interconnection element is affixed to post 1650,the tip structure is separated from sacrificial substrate 110 at releaselayer 125. In the example where release layer 125 is aluminum, onemethod of separating the tip from sacrificial substrate 110 is byreacting release layer 125 with a sodium hydroxide (NaOH) solution. FIG.16( b) shows the final interconnection element coupled to electroniccomponent 1010. Any remaining unwanted seed material 130 adjacent firsttip material 137 may be removed with a subsequent etch or retained ascontact material.

Instead of separating the interconnection element containing a tipstructure and a body from sacrificial substrate 110, a sixth aspect ofan embodiment of the invention contemplates the forming of a post forthe interconnection element on the sacrificial substrate. FIGS. 17(a)-17(e) illustrate this process.

FIG. 17( a) shows structure 100 of FIG. 15( f) after the patterning ofpost masking material layer 199 over structure 100 including an openingto the inferiorly located leaf portion (leaf portion defined byconductive material 170) at the proximal end of conductive material 170(i.e., proximal relative to the location of the tip structure of theinterconnection element on the end of the leaf portion definedprincipally by reference numeral 155). Post masking material 199 is, forexample, photoresist material similar to other masking material layers.Prior to patterning post masking material layer 199, an adhesion/seedlayer may be patterned over leaf portion 170 similar, in one embodiment,to adhesion/seed layer 145 described above. As noted above, thedescribed adhesion/seed layers facilitate, in one aspect, anelectrolytic process of introducing interconnection material. It is tobe appreciated that such adhesion/seed layers may not be necessary,particularly where the masking material that is used to fabricate theinterconnection element is conductive material. One example of such aprocess is described with reference to FIGS. 34-52 and the accompanyingtext.

Post masking material layer 199 is, for example, photoresist materialsimilar to other masking material layers (e.g., first masking materiallayer 135, second masking material layer 150, third masking materiallayer 158, fourth masking material layer 161, fifth masking materiallayer 164, sixth masking material layer 167, seventh masking materiallayer 168, and eighth masking material layer 171). Post masking materiallayer 199 is patterned to a suitable height for a post of aninterconnection element including consideration for a subsequentplanarization step to define the height of the post. The thickness ofpost masking material layer 199 will primarily determine the distancethat the main body portion (i.e., spring and tip) of the interconnectionelement is spaced away from the surface of an electronic component. Inan example where resiliency is desired, the dimension of the post, thebody, and the tip structure may be coordinated to maximize the contactforce of the tip structure with, for example, a terminal of anelectronic component, and minimize the potential “bottoming out” of thedeflected body. For current technologies according to the methoddescribed, a suitable height of post masking material 199 isapproximately 1-30 mils (25-750 μm), and preferably 3-8 mils (75-200μm).

FIG. 17( b) shows structure 100 after introducing post material 205 inthe opening and post masking material layer 199 via, for example, anelectroplating process. In one example, post material 205 isnickel-cobalt similar to the body of the interconnection element (e.g.,first body material 155, second body material 163, third body material166, and fourth body material 170). Post material 205 is preferablyintroduced to a thickness of at least the thickness of post maskingmaterial layer 199, and generally greater than the thickness of postmasking material layer 199 (e.g., overplating).

FIG. 17( c) shows structure 100 after planarizing post material 205 andpost masking material layer 199 to define a desired thickness for thepost of the interconnection element. The planarization may beaccomplished in a manner similar to the planarization proceduresdescribed above.

FIG. 17( d) shows structure 100 after removing the masking materiallayers. In the example where the various masking material layers (e.g.,first masking material layer 135, second masking material 150, thirdmasking material layer 158, fourth masking material layer 161, fifthmasking material layer 165, sixth masking material layer 167, seventhmasking material layer 168, eighth masking material layer 171 and postmasking material layer 199 illustrated together in FIG. 17( c)) arephotoresist, an oxygen ashing, reactive ion etching, laser ablation orwet chemical etch step may be used to remove the masking materiallayers. The removal of the masking material layers leaves theinterconnection element affixed at its tip structure to sacrificialsubstrate 110 as shown in FIG. 17( d).

One technique for mounting the interconnection element shown in FIG. 17(d) to an electronic component is by retaining the interconnectionelement on the sacrificial substrate as shown in FIG. 17( d) andaligning post 205 with a corresponding terminal on an electroniccomponent, whereupon post 205 may be suitably soldered, brazed, welded,etc., to a contact pad or terminal. It is to be appreciated that anysuitable technique and/or material for affixing the post of theinterconnection element to a contact pad or terminal of an electroniccomponent may be employed. Once the interconnection element is affixedto an electronic component, sacrificial substrate 110 may be removed ina suitable manner, such as the dissolution of release layer 125 bysodium hydroxide (NaOH), chemical etching, heating, etc. Any remainingunwanted seed material layer 130 adjacent first tip material 130 may beremoved with a subsequent etch or retained as contact material.

FIG. 17( e) shows the interconnection element having tip structure 201of first tip portion 137 and second tip portion 140, body 200, and post205 coupled to contact pad or terminal 212 of electronic component 210.Electronic component 210 is, for example, a space transformer of a probecard assembly or another integrated circuit. Electronic component 210is, for example, a semiconductor- or ceramic-based substrate havingcontact pads or terminals on opposing surfaces. In the case of acommercially available ceramic-based electronic component 210, forexample, the electronic component includes terminals 212 and 215 onopposing surfaces of the electronic component. Terminals 212 and 215 areconnected, for example, to conductive circuits 216 running through theelectronic component such as, for example, a molybdenum or tungsten ormolybdenum/tungsten circuit. Terminals 212 and 215 on electroniccomponent 210 are, for example, copper, nickel, and gold terminals thatmay be suitable for connecting to an interconnection element by, forexample, soldering. In one example, the copper facilitates theelectroplating process and is the upper layer. The nickel acts a barrierbetween the gold and the copper.

FIG. 17( e) shows an interconnection element having body 200 of fourleaf portions. Adjacent leaf portions are coupled to one another attheir proximal ends to form a cantilever spring. The area at which theleaf portions are coupled is represented by supports 202. In theembodiment described supports 202 comprise a portion of adhesion/seedlayer and a portion of body material selected to comprise a sufficientthickness to resist bending forces and maintain structural integrity.Spacing is provided by gaps 201 where masking material was originallydeposited, as described above. It is to be appreciated that, accordingto this embodiment, supports 202 may be fabricated as discretestructures apart from the fabrication of a subsequent leaf portion suchas, for example, by introducing and seeding an opening of a maskingmaterial and depositing a conductive material for supports 202.Planarization of the masking material and the conductive material mayalso be desirous. The thickness of supports 202 may also be varied.

As is evident in FIG. 17( e) (and FIGS. 14( c) and 16(b)), a pluralityof elongate or cantilever interconnection elements such as described canbe affixed to an electronic component having a plurality of contacts orterminals on the surface thereof. In this embodiment, eachinterconnection element has a post, a body, and a tip structure oppositethe post. Each interconnection element is affixed at its post to acorresponding contact pad or terminal of an electronic component. Thetip structure of each interconnection element extends above the surfaceof the electronic component to a position that is laterally and/ortransversely offset from the post forming a free standing, cantileverstructure. When affixed to an electronic component, the interconnectionelement of the invention has a height of “L2,” this being the distancebetween the highest portion of the tip structure and the inward-mostportion where the post is affixed to electronic component 210. Arepresentative height, L2, for an interconnection element according tocurrent technologies is, for example, 10-20 mils and will depend, inpart, on considerations of contact pad or terminal spacing on anelectronic component to be contacted or probed by an array ofinterconnection elements, deflection distance of the interconnectionelement, and the spring constant of the interconnection element.

In FIG. 17( e), the distance between the underside of theinferiorly-located leaf portion of body 200 and the surface ofelectronic component 210 represents the distance that theinterconnection element can deflect (absent any stops) in response to acompressive force applied at the tip structure. The height of post 205and contact pad or terminal 212 (and any bonding material thickness)primarily determines this distance. A similar relationship appliesbetween the superiorly-located leaf portion of body 200 and the end oftip 201. Reference is made to FIG. 4 and the accompanying text thatdescribe the travel of the interconnection element.

The above embodiments described an interconnection element coupled to asubstrate that is or is part of an electronic component and theinterconnection element serves as a conductive path from a contact pador terminal. It is to be appreciated that the interconnection element ofthe invention need not be coupled to a contact pad or terminal and neednot serve as a conductive path. Instead, an interconnection element thatis, for example, a mechanical spring is also contemplated.

The lithographic technique of forming an interconnection element on asacrificial substrate is representative of one technique of forming theinterconnection elements of the invention. A second technique where theinterconnection element is formed directly on an electronic component isalso contemplated. Reference is made to patent application Ser. No.09/205,022 filed Dec. 2, 1998 entitled “Lithographic Contact Elements,”and patent application Ser. No. 09/205,023 filed Dec. 2, 1998 entitled“Lithographic Contact Elements,” co-owned by the assignee of theinvention described herein, which describe such a technique and whichare incorporated by reference. It is to be appreciated that thetechniques described herein of forming interconnection elements having abody with a plurality of leaf portions can be incorporated into thediscussions of forming interconnection elements on an electroniccomponent described in these other applications.

B. Exemplary Applications of Spring Interconnect Structures

FIG. 18 illustrates an application wherein a plurality ofinterconnection elements 500 such as those described hereinabove arearranged on a substrate such as a space transformer of a probe cardassembly and affixed thereto in the manner described hereinabove, sothat their tip structure ends are disposed in a manner suitable formaking contact with the bond pad of a semiconductor device having itscontact pads or terminals arranged along its periphery. This applicationis similar to the application described in co-pending, commonly-ownedU.S. patent application Ser. No. 08/802,054, titled “MicroelectronicContact Structure, and Method of Making Same.” In FIG. 18, eachinterconnection element 500 includes post 502 (denoted by “x”) and tipstructure 504 and is mounted to an electronic component such as a spacetransformer (schematically illustrated by the dashed line 510) of aprobe card assembly. Tip structures 504 are arranged in a pattern,mirroring the pattern of contact pads or terminals 522 (illustratedschematically by circles) of an electronic component (schematicallyillustrated by dashed line 520) such as a semiconductor device.Interconnection elements 500 “fan-out” from their tip structures 504, sothat each of their posts 502 is disposed at a greater pitch (spacingfrom one another) than their tip structures 504.

FIG. 19 illustrates another application (also similarly described inco-pending, commonly-owned U.S. patent application Ser. No. 08/802,054)wherein a plurality of interconnection elements 600 such as thosedescribed hereinabove are arranged on a substrate such as a spacetransformer of a probe card assembly and affixed thereto in the mannerdescribed hereinabove, so that their tip structures are disposed in amanner suitable for making contact with the contact pads or terminals ofa semiconductor device having its contact pads or terminals arranged ina row along a center line thereof. In FIG. 19, each interconnectionelement, generally denoted by reference numeral 600, includes post 602(denoted by “x”) and tip structure 604, and are mounted to an electroniccomponent such as a space transformer of a probe card assembly(schematically illustrated by dashed line 610). Tip structures 604 arearranged, in a pattern mirroring that of contact pads or terminals 622(illustrated schematically by circles) of an electronic component(schematically illustrated by dashed line 620) such as a semiconductordevice. In this example, the pitch of contact pads or terminals 622 inan xy-direction is 2 mils (50.8 μm) by 1.414 mils (35.9 μm),respectively. Interconnection elements 600 are arranged in the followingsequence. First interconnection element 600 a is relatively short (e.g.,has the length in an x-direction of, in this embodiment, approximately60 mils (1524 μm)), and is disposed to extend towards one side (right,as used) of electronic component 620. Second interconnection element 600b is adjacent first interconnection element 600 a and is also relativelyshort (e.g., a length in an x-direction of, in this embodiment,approximately 60 mils (1524 μm)), and is disposed to extend towards anopposite side (left, as used) of electronic component 620. Thirdinterconnection element 600 c is adjacent second interconnection element600 b and is relatively long (e.g., has a length in an x-direction of,in this embodiment, approximately 80 mils (2032 μm)), and is disposed toextend towards the one side (right, as used) of electronic component620. Finally, fourth interconnection element 600 d is adjacent thirdinterconnection element 600 c and is also relatively long (e.g., has alength in an x-direction of, in this embodiment, approximately 80 mils(2032 μm)), and is disposed to extend towards the opposite side (left,as used) of electronic component 620. In this manner, tip structures 604are disposed at a fine pitch commensurate with that of contact pads orterminals 622, and posts 602 are disposed at a significantly greaterpitch from one another.

FIG. 20( a) shows a third application wherein a plurality ofinterconnection elements 715 such as those described hereinabove arearranged on a substrate such as electronic component 720 (shown indashed lines) and affixed thereto in the manner described hereinabove,to accommodate the contacting of a densely packed array of contact padsor terminals 710 on electronic component 700. In this embodiment,interconnection elements 715 are arranged in a diagonal array in an x-yplane over contact pads or terminals 710 to accommodate a pitch betweencontact pads or terminals 710 that is not suitable for a longitudinallyor laterally extending array of interconnection elements.Interconnection elements 715 are arranged over contact pads or terminals710 such that the tip structures of interconnection elements 715 contactthe contact pads or terminals 710. Posts 725 are located at the proximalend of the rectangular body of interconnection elements 715. Asillustrated in FIG. 20( a), in one embodiment, interconnection elements715 are arranged in a non-aligned relation relative to their contactingof contact pads or terminals 710 in the same row of electronic component700.

FIG. 20( b) illustrates an application wherein a plurality ofinterconnection elements 716 such as those described hereinabove arearranged on a substrate such as electronic component 721 (shown indashed lines) and affixed thereto in the manner described hereinabove,to accommodate the contacting of a densely packed array (3 across) ofcontact pads or terminals 711 on electronic component 701. Asillustrated in FIG. 20( b), in one embodiment, interconnection elements716 are arranged in an aligned relation relative to their contacting ofcontact pads or terminals 711 in the same row of electronic component701.

FIG. 20( a) and FIG. 20( b) illustrate that the length (“l”) and width(“w”) of an individual interconnection element may be limited by thespacing of contact pads or terminals 710. To maintain the desired springconstant, deflection distance, and a material stress less than themaximum stress, interconnection elements 715 or 716 must be increased inthe z-direction (coming out of page of FIG. 20( a) and FIG. 20( b)). Themultiple leaf portion body of the interconnection element of theinvention accommodates this requirement.

C. Exemplary Layouts of Spring Interconnect Structures

By using photolithographic techniques as described above, theinterconnection elements according to the invention may be fabricatedwith an area array pitch corresponding to the reduced pitch ofstate-of-the-art electronic components. Accordingly, the interconnectionelements according to the invention are well-suited to the fine-pitch,close-tolerance environment of micro-electronic components. FIGS. 21(a)-21(b) illustrate one layout where pitch between adjacentinterconnection elements may be further minimized. FIGS. 21( a) and21(b) show two different views of adjacent interconnection elements 740Aand 740B. Adjacent interconnection elements 740A and 740B may befabricated directly on an electronic component or on a sacrificialsubstrate and transferred to an electronic component similar to theprocess steps above with respect to FIGS. 7-17( e) and the accompanyingtext. In this embodiment, adjacent interconnection elements are stackedat slight angles to separate the tip structures. As interconnectionelements are depressed, the body of the adjacent interconnectionelements do not contact each other, at least in one embodiment.

Interconnection element 740A includes post 730A, body 745A and tipstructure 760A. Interconnection element 740B includes post 730B, body745B and tip structure 760B. As a further enhancement, interconnectionelement 740B includes spacers 732B and 733B to align interconnectionelement 740B at a similar height (in a z-direction) as interconnectionelement 740A. Interconnection element 740A also includes spacers 731Aand 732A to separate, in this example, body 745A of interconnectionelement 740A from underlying interconnection element 740B. In the mannerwhere interconnection elements 740A and 740B are formed simultaneously,spacer 733B of interconnection element 740A and body 745A ofinterconnection element 740B may be patterned and formed simultaneously.It is to be appreciated that, according to this method, spacer 733B willbe formed through the same multiple pattern masking, seeding,deposition, and planarization steps as body 745A. Thus, spacer 733B willbe a composite of seed material and conductive material.

Spacers 732A and 732B may be patterned in the same masking materiallayer (e.g., a masking material layer patterned after seeding an areaover body 745A and an area corresponding to subsequently formed body745B). Spacers 732A and 732B are optional and can be reduced in size toprovide, in one aspect, clearance as the interconnection elements aredeflected. To the extent they are present, spacers 732A and 732B may beformed of the same conductive material deposition. Spacer 731A ispatterned and formed at the same time as body 745B of interconnectionelement 740B. According to this method, spacer 731A will be formedthrough the same multiple pattern masking, seeding, deposition, andplanarization steps as body 745B. Thus, spacer 731A will be a compositeof seed material and conductive material.

In this embodiment, using photolithographic techniques, the length ofthe rectangularly-shaped body 745A and 745B of adjacent interconnectionelements 740A and 740B, respectively, may be varied. Adjacentinterconnection elements 740A and 740B are fabricated along the sameaxis (e.g., x-axis) at their posts (post 730A and 730B) and along asecond axis (e.g., y-axis) at their tip structures (tip structures 760Aand 760B). As noted, body 745A of interconnection element 740A ispatterned directly over post 730B of interconnection element 740B.Accordingly, in an x-direction, the posts (730A and 730B) are axiallyaligned. At the tip structure of each interconnection element (760A and760B), interconnection elements 740A and 740B are axially aligned alonga y-axis. Thus, FIGS. 21( a) and 21(b) show adjacent interconnectionelements that have a greater pitch between their tip structures thantheir posts. Such a configuration is suitable, for example, to generatean electronic component with a plurality of interconnection elements forprobing a second electronic component having its contact pads orterminals arranged along its periphery and having an ultra-fine pitch.It is to be appreciated that the actual pitch between posts and tipstructures according to this embodiment can vary to accommodate thepitch of contact pads or terminals on an electronic component to becontacted.

FIG. 21( c) and FIG. 21( d) describe a second orientation of adjacentinterconnection elements according to an embodiment of the invention.Interconnection element 840A includes post 830A, body 845A, and tipstructure 860A. Interconnection element 840A also includes spacers 831Aand 832A formed over post 830A. Spacers 831A and 832A, in this example,separate body 845A from underlying interconnection element 840B. In oneembodiment, the spacer is designed so the springs remain separatethroughout a range of simultaneous displacement. Interconnection element840B includes post 830B, body 845B, and tip structure 860B.Interconnection element 840B further includes spacers 832B and 833B thatalign tip structure 860B with tip structure 860A of interconnectionelement 840A along a z-axis (similar height). In FIGS. 21( c) and 21(d),interconnection elements 840A and 840B are axially aligned at both theirposts and their tip structures.

Using photolithographic techniques, the rectangularly-shaped body ofeach of the adjacent interconnection elements in FIGS. 21( c) and 21(d)is fabricated to approximately the same length and the resultinginterconnection element is offset by the distance between the postsalong the same axis. Such a configuration is suitable, for example, togenerate an electronic component with a plurality of interconnectionelements for probing a second electronic component having its contactpads or terminals arranged in an ultra-fine pitch row along a centerline thereof. Again, it is to be appreciated that the actual pitchbetween posts and tip structures according to this embodiment can varyto accommodate the pitch of contact pads or terminals of an electroniccomponent to be contacted.

FIG. 21( e) and FIG. 21( f) illustrate still further arrangements usingsimilar overlaying patterning techniques for forming interconnectionelements as described with reference to FIGS. 21( a)-21(d). FIG. 21( e)shows a plurality of interconnection elements formed according to thetechniques described hereinabove, arranged on an electronic component(not shown). Interconnection elements 900A, 900B, 900C, and 900D arearranged so that their corresponding tip structures 960A, 960B, 960C,and 960D, respectively, are aligned in a y-direction while posts 930A,930B, 930C, and 930D are staggered in an x-direction. FIG. 21( f) showsa second configuration wherein a plurality of interconnection elements980A, 980B, 980C, and 980D are arranged on an electronic component (notshown) so that their corresponding tip structures 985A, 985B, 985C, and985D, respectively are staggered in an x-y direction as are theircorresponding posts 990A, 990B, 990C, and 990D, respectively. In thisexample, respective posts are larger (have a greater xy profile) thanthe tip structures in this embodiment.

The methods of forming interconnection elements described above usinglithographic techniques including multiple masking and planarizationsteps should not be interpreted as limiting the scope of the invention.It is to be appreciated, that there are other ways of forminginterconnection elements to accommodate, for example, dense contact pador terminal arrays of electronic component device geometries. Thelithographic formation including planarization steps described abovepermit the consistent formation of interconnection elements, includingcantilever spring interconnection elements, having similar size andmechanical (e.g., compliance) properties. It is to be appreciated,however, that there may be other ways of forming interconnectionelements, including multiple leaf portion interconnection elements thatare suitable for the applications contemplated by the invention.

D. Exemplary Body Portions of Spring Interconnect Structures

The above description of forming interconnection elements of theinvention is related generally to the formation of cantilever springinterconnection elements having a generally rectangular body withmultiple leaf portions. It is to be appreciated, that the invention isnot limited to interconnection elements having generally rectangularbodies. FIGS. 22( a)-23(b) show various representative, usefulconfigurations for leaf portions of the body of an interconnectionelement formed, for example, on sacrificial substrate 110. It is to beappreciated that there may be various other configurations suitable forparticular applications for the interconnection elements of theinvention. FIGS. 22( a)-23(b) are to be viewed as representative ofthese various configurations. Like reference numerals from the structureformed in FIGS. 7-17( e) are used to indicate like components and/ormaterials where appropriate. It is also to be appreciated that, certainproperties of an interconnection element adopting leaf portions havingone or more of these alternative configurations, will differ from therectangular beam structure described above. For example, in calculatingthe maximum stress under load of the tapered structures illustrated inFIG. 22( a) through FIG. 22( g), the width of the leaf portion should beconsidered.

FIG. 22( a)-22(g) show top planar views of various configurations of aleaf portion of an interconnection element formed on substrate 110 in anxy plane. FIG. 22( a) shows, for example, first body material 155 aconfigured to have a taper in the y-direction (“y-taper”) as thematerial laterally extends (in an x-direction) from an area over thesurface of, for example, second tip material 140. This configurationmore evenly distributes the stress on the interconnection element byreducing the size of the extremity of the leaf portion (e.g., thecantilever body) of the interconnection element. In FIG. 22( a), alaterally extending portion of first body material 155 a is depictedwith substantially linear edges. It is to be appreciated that the edgesneed not be substantially linear but may be curved such as, for example,in a concave manner. FIG. 22( b) shows laterally extending first bodymaterial 155 b with substantially convex edges. The patterning of themasking material layer, such as first masking material layer 135,dictates the shape of the leaf portion.

FIG. 22( c) shows a third configuration of a leaf portion of aninterconnection element in accordance with a first embodiment of theinvention. In this configuration, first body material 155 c extendslaterally (in an x-direction) and transversely (in a y-direction) from,for example, second tip material 140 to form a curved leaf portion.FIGS. 22( d) and 22(e) show a fourth and a fifth configuration,respectively, where a leaf portion 155 d and 155 e, respectively, extendlaterally and transversely. The laterally and transversely extendingleaf portions may be desirous, for example, when fabricatinginterconnection elements to particularly minimize the pitch betweenadjacent interconnection elements. FIG. 22( f) shows a sixthconfiguration of a leaf portion wherein first body material 155 fpartially encircles second tip material 140. FIG. 22( g) shows a seventhconfiguration of a leaf portion having an “S” shape in an xy plane.Again, the patterning of the masking material layer will dictate theshape of leaf portion of first body material 155 g.

FIG. 23( a) and FIG. 23( b) show eighth and ninth configurations,respectively, of a leaf portion of the interconnection element inaccordance with an embodiment of the invention in an xz plane. FIG. 23(a) shows first body material 155 g having a planar upper surface and aconcave lower surface. FIG. 23( b) shows first body material 155 hhaving a planar superior surface and a linearly increasing inferiorsurface toward the extremity to form a beveled leaf portion. First bodymaterials 155 g and 155 h can be formed in this manner in a number ofways, including varying the light source to shape the underlying andadjacent photoresist that forms the masking material and electroplatingin the presence of a resistive layer mask to distribute theelectroplated material where desired.

The above description relates primarily to interconnection elementshaving a body of cantilever leaf portions of similar dimension. It is tobe appreciated that other configurations for the leaf portions arecontemplated. The following figures are representative of the variousconfigurations contemplated by the invention. Each of the differentconfigurations may be formed using the formation techniques describedabove with reference to FIGS. 7-17( e) with variations in one or more ofthe masking layer patterning, the body layer depositions, and theplanarization steps.

FIG. 24( a) and FIG. 24( b) illustrate an embodiment of aninterconnection element having a body of leaf portions of variousdimensions. In FIG. 24( a), interconnection element 1800 includes post1810, body 1805, and tip structure 1815. Body 1805 includes four leafportions 1801, 1802, 1803, and 1804. In this embodiment, the length andthe thickness of each leaf portion is varied. Thus, the length of leafportion 1801, “l₁,” is shorter than the length of second leaf portion1802, “l₂,” which is shorter than the length of leaf portion 1803, “l₃,”which is shorter than the length of leaf portion 1804, “l₄.” “Thethickness of first leaf portion 1801, “t₁,” is similarly less than thethickness of second leaf portion 1802, “t₂,” which has a material stressless than the maximum stress for a desired deflection distance, and isless than the thickness of third leaf portion 1803, “t₃,” which is lessthan the thickness of fourth leaf portion 1804, “t₄.” FIG. 24( b) showsinterconnection element 1800 subjected to a force at tip structure 815and illustrates the compliance of body 1805. An opposite configuration(i.e., shorter is thicker) is also contemplated for the situation wherea similar spring constant is desired among the leaf portions.

FIG. 25( a) and FIG. 25( b) show another alternative configuration forthe interconnection element of the invention. In FIG. 25( a),interconnection element 1820 includes post 1822, tip structure 1823, andbody 1825. Body 1825 includes four leaf portions 1821 a, 1821 b, 1821 c,and 1821 d of similar length each having a proximal and a distal end.Tip structure 1823 is coupled at the distal end of superiorly-locatedleaf portion 1821 a. Post 1822 is coupled at the distal end ofinferiorly-located leaf portion 1821 d. Supports 1824 coupled theadjacent leaf portions staggers between either the proximal end or thedistal end of adjacent leaf portions. FIG. 25( b) shows theinterconnection element of FIG. 25( a) with a force applied at tipstructure 1823. The deflection of interconnection element 1820 willgenerally not result in significant wiping of a contact pad or terminal.

FIG. 26( a) and FIG. 26( b) show yet another configuration for theinterconnection element of the invention. In FIG. 26( a),interconnection element 1830 includes post 1832, tip structure 1833, andbody 1835. Body 1835 includes three leaf portions 1831 a, 1831 b, and1831 c separated by supports 1834. In this configuration, tip structure1833 is aligned with post 1832. The individual length of leaf portion1831 b is greater than either leaf portion 1831 a or leaf portion 1831b. FIG. 26( b) shows the interconnection element of FIG. 26( a) with aforce applied at tip structure 1833. The deflection of interconnectionelement 1830 will generally not result in significant wiping of acontact pad or terminal.

FIG. 27( a) and FIG. 27( b) show another embodiment of theinterconnection element of the invention. FIG. 27( a) showsinterconnection element 1830 including post 1832, tip structure 1833,and body 1835. Body 1835 includes, in this case, two leaf portions. Eachleaf portion is coupled to the adjacent leaf portion by supports 1834and 1836 at a proximal end and at a distal end, respectively. Thethickness of the superiorly-located leaf portion is greater than thethickness of the inferiorly-located leaf portion (t₁>t₂). FIG. 27( b)shows the structure of FIG. 27( a) after subjecting the interconnectionelement to a force at tip structure 1833. FIG. 27( b) shows that theinferiorly-located leaf portion of body 1835 buckles at point 1837 inresponse to the force applied at tip structure 1833. In this embodiment,the buckling is facilitated by the inferiorly-located leaf portionhaving a thickness less than the other leaf portion of body 1835. Thebuckling action may permit a reduction in the number of leaf portionsnecessary to achieve a desired deflection for a unit force. With thisconfiguration, the wiping of the interconnection element against acontact pad or terminal in response to a force applied to the tipstructure of interconnection element 1830 may be less than a cantileverconfiguration.

FIG. 28( a) and FIG. 28( b) show still another configuration for aninterconnection element of the invention. In FIG. 28( a),interconnection element 1840 includes post 1842, tip structure 1843, andbody 1835. Body 1835 includes, in this case, three leaf portions 1846,1847 and 1848. The superior and inferior surfaces of the leaf portionsmay be a rectangular beam, including squares, with or without an openingtherethrough. Adjacent leaf portions are separated by supports 1849.Supports 1849 are arranged in staggered fashion between adjacent leafportions. FIG. 28( b) shows interconnection element 1840 with a forceapplied at tip structure 1843. FIG. 28( b) shows that thestaggeredly-coupled leaf portions bow in opposite directions resultingin no wiping of the tip structure of the interconnection element againsta contact pad or terminal.

FIGS. 29( a)-29(d) illustrate a further embodiment of an interconnectionelement according to the invention. FIG. 29( a) shows a planar sideview, FIG. 29( b) a second planar side view, and FIG. 29( c) shows aperspective top view of interconnection element 1850 having post 1852,tip structure 1853, and body 1855. In this embodiment, body 1855includes four leaf portions 1856, 1857, 1858, and 1859 that are eachcylindrical leaf portions having, with the exception of leaf portion1856, an opening therethrough. The cylindrically-shaped leaf portionsare coupled to one another through staggered supports 1854. It is to beappreciated that the individual masking material layers may be modifiedto pattern cylindrical leaf portions as well as staggered supports orcoupling. FIG. 29( d) shows interconnection element 1850 having a forceapplied at tip structure 1853. FIG. 29( d) schematically illustrates thedeformation of the leaf portions in response to a force applied at tipstructure 1853 of body 1855 resulting in no wiping against a contact pador terminal. Unlike interconnection elements having a plurality ofcantilever leaf portions, there generally is no “travel-to-contact”component whereby a displaced leaf portion travels a distance to contactan adjacent leaf portion. Instead, an interconnection element of aplurality of cylindrical leaf portions behaves like a coil spring inthat the leaf portions will continuously deform until the leaf portionsstrike one another at a maximum deflection.

It is to be appreciated that a cylindrical or other leaf portion may ormay not have an opening therethrough. In the situation where an openingis desired, the opening may or may not be circular. FIG. 30 shows leafportion 1855 with a “clover-leaf” opening therethrough.

In general, the behavior of interconnection elements having stackedcylindrical leaf portions is different than the behavior ofinterconnection elements having layered cantilever leaf portionsdescribed above. Each cylindrical leaf portion has a spring constant, k,and a deflection to reach maximum stress. The spring constant of thestacked cylindrical interconnection element is determined by the springconstant of an individual leaf portion (k=k_(leaf)) and the maximumdeflection is determined by the deflection distance of the total numberof individual leaf portions: σ_(max)=n·δ_(leaf), where n is the numberof leaf portions. This differs, for example, from a stacked rectangularleaf portion like that of FIG. 3 (e.g., cantilever) interconnectionelement where the spring constant is determined by the number of leafportions (k=n·k_(leaf)) and the maximum stress by the deflectiondistance of a leaf portion: σ_(max)=δ_(leaf).

FIG. 31 illustrates still a further embodiment, where leaf portion 1870of a body of interconnection element is “H”-shaped with supports 1875patterned at diagonals from one another. Such a pattern will tend tostress the material by working the middle portion of the “H”-shape in atorsional manner, in response to a load or force applied to theinterconnection element. The reduction in stress will permit a reductionin the number of leaf portions necessary for a desired deflection. FIG.32 shows leaf portion 1880 having a rectangular configuration with anopening therethrough and support portions 1885 at diagonals. It is to beappreciated that there are many other configurations in addition to theones described above. Accordingly, the examples of interconnectionelements and leaf portions described should be regarded in an exemplaryrather than a restrictive sense.

E. Alternative Applications of Spring Interconnect Structures

In addition to the uses of the interconnection element of the inventionas an interconnection element between two electronic components, FIGS.33( a)-33(c) show an embodiment where adjacent interconnection elementsform a switch, e.g., a micro-switch, or a detector. FIG. 33( a) shows aside view of adjacent interconnection elements 1905 and 1915. FIG. 33(b) is a top perspective view of interconnection elements 1905 and 1915.FIG. 33( c) is a top view of interconnection elements 1905 and 1915.

Interconnection element 1905 includes post 1925 coupled to contact pador terminal 1930 on electronic component 1900. Interconnection element1905 also includes spring 1910 of a plurality (e.g., three) of leafportions coupled to post 1925. The inferior leaf portion includeslaterally extending tab portion 1950.

Interconnection element 1915 includes post 1930 coupled to contact pador terminal 1940 on electronic component 1900. Interconnection element1915 also includes body 1920 of, in this example, a single beam, coupledto post 1930.

Interconnection element 1905 and interconnection element 1915 may beformed according to techniques described above, for example, with regardto the formation of interconnection elements according to FIGS. 21(a)-21(d) and the accompanying text. Modifications regarding maskingmaterial openings and body (e.g., conductive) material deposition areaccommodated to account for the alignment of the interconnectionelements on electronic component 1900, for tab portion 1950 ofinterconnection element 1905, and for the differences in body portionsof the respective interconnection elements. Such modifications will beunderstood by those of ordinary skill in the art based on the teachingsdiscussed above and are therefore not presented herein.

Interconnection element 1905 and interconnection element 1915 have beenillustrated and described without a tip structure. The embodimentdescribed with reference to FIGS. 33( a)-33(c), as with the otherembodiments of interconnection elements described herein, does notrequire a tip structure to function. The tip structure in otherembodiments defined herein offers one contact point for theinterconnection element. It is to be appreciated that this contact pointneed not be established by the interconnection element, but can beestablished by an external source such as an electronic component orother substrate or structure contacting the interconnection element. Forexample, a contact point may be in the form of a traditional pad, apost, a pointed post, or other structure.

Referring to FIGS. 33( a)-33(c), tab portion 1950 laterally extends frombody 1910. Tab portion 1950 is separated from a superior surface of body1920 of interconnection element 1915 by a distance, lc.

When a force, F, is applied to the superior surface of body 1910, body1910 is deflected toward the surface of electronic component 1900.Initially body portion 1910 a is deflected. Body portion 1910 a contactsbody portion 1910 b and deflects body portion 1910 b toward electroniccomponent 1900. Further deflection causes body portion 1910 b to contactbody portion 1910 c and deflect body portion 1910 c toward electroniccomponent 1900.

Tab portion 1950 extends from body portion 1910 c and is adapted tocontact the superior surface of body 1920 upon sufficient deflection ofbody portion 1910 c. The contacting of tab portion 1950 with a superiorsurface of body 1920 acts, in one sense, as a switch to, for example,close a circuit between the interconnection elements. Alternatively, theelectrical interconnection between adjacent bodies 1910 and 1920 may beused to detect a capacitance between two electrodes. The capacitance canbe correlated to a distance.

In one case, body 1920 may be fairly rigid and the deflection of tabportion 1950 onto body 1920 does not cause body 1920 to significantlydeflect toward the surface of substrate 1900. This is shown in theembodiment illustrated in FIGS. 33( a)-33(c) wherein body 1920 ofinterconnection element 1915 is more robust, particularly in thez-direction, than the leaf portions of body 1910 of interconnectionelement 1905. The deflection of body 1910 toward the surface ofsubstrate 1900 may be limited by, for example, a travel stop.Alternatively, body 1920 of interconnection element 1915 may deflecttoward the surface of substrate 1900 in response to a force such as aforce applied by tab portion 1950 of interconnection element 1905. Insuch case, body 1920 of interconnection element 1915 may be comprised ofa plurality of leaf portions. Finally, body 1920 may itself include atab portion to, upon deflection, contact another interconnection elementor a terminal, for example, to close a circuit. In this manner, a devicesuch as a tiered-relay may be formed.

In the above embodiment, mechanical and electrical contact wasestablished between two adjacent interconnection elements. It is to beappreciated that mechanical and electrical contact may also beestablished in one interconnection element so that the interconnectionitself acts as a switch. One way this may be accomplished is forming aninterconnection element similar to the interconnection elementsdescribed above with reference to FIGS. 7-17 e and the accompanying textand electrically isolating one or more leaf portions of theinterconnection elements. The application of a force to the body of theinterconnection element will cause the isolated leaf portion(s) tocontact other leaf portions and electrical contact.

F. Alternative Fabrication Techniques of a Multi-Leaf or Multi-TierSpring Interconnection Element

FIGS. 34-52 illustrate a second fabrication technique of forming amultiple leaf portion spring interconnection structure. As the startingpoint for this embodiment, a structure similar to the structure shown inFIG. 10 is presented. FIG. 34 shows structure 2110 that is, for example,a sacrificial substrate such as a semiconductor substrate. Substrate2110 has a pyramidally-shaped depression formed therein as an outlinefor a portion of a tip structure to be formed. Overlying the surface ofsubstrate 2110 is release layer 2125 of, for example, a metal such asaluminum deposited to a thickness of approximately 5,000 angstroms usingconventional deposition techniques. Overlying release layer 2125 on thesurface of substrate 2110 is seed layer 2130. Seed layer 2130 is, forexample, copper, palladium, or titanium-tungsten that establishes anappropriate potential for an electrolytic process. Overlying seed layer2130 is first masking material layer 2135. First masking material layer2135 is, for example, a photopolymer (e.g., a negative photoresist)introduced onto the surface of substrate 2110 to a thickness of thedesired height of a tip structure of an interconnection element takinginto consideration the possibility of planarizing a portion of firstmasking material 2135 with tip structure material. Approximately 1-4mils (25-100 μm) is a useful height range. First masking material layer2135 is patterned to have an opening over the pyramidally-shapeddepression in substrate 2110. Alternatively, first conductive materiallayer mask 2150 may be introduced as a plurality of traces, each tracecorresponding to an area over substrate 2110 as well as the tipstructure formed in substrate 2110 where a body of an interconnectionelement is to be formed to serve, in one manner, as an electroformwhereupon the body can be fabricated.

FIG. 34 also shows tip structure material introduced onto substrate2110. Similar to the tip structure material described above withreference to FIG. 9 and FIG. 10 and the accompanying text, the tipstructure material includes first tip material 2137 of, for example,palladium, gold, rhodium and their alloys, including, but not limitedto, alloys of nickel and cobalt introduced to a thickness of about 1 to5 μm or more—even tens of microns or more. Suitable introductiontechniques include, but are not limited to, electroplating, chemicalvapor deposition, sputter deposition, and electroless plating. The tipstructure also includes second tip material 2140 of, for example, analloy of nickel and cobalt introduced to a height approximating theheight of first masking material layer 2135.

FIG. 35 shows structure 2000 after the removal of first masking materiallayer 2135. In embodiment, wherein first masking material layer is aphotoresist, first masking material layer 2135 may be removed by anetch, reactive ion etching, laser ablation, or wet etching.

FIG. 36 shows structure 2000 after the introduction of first conductivematerial layer mask 2150. First conductive material layer mask 2150 is,for example, a metal such as copper introduced by an electrolyticprocess. First conductive material layer mask 2150 is conformallyintroduced over the surface of substrate 2110. First conductive materiallayer mask 2150 may be introduced by way of a blanket deposition oversubstrate 2110. Alternatively, first conductive material layer mask 2150may be introduced as multiple, non-contiguous regions or traces, eachregion corresponding to an area over substrate 2110 as well as the tipstructure formed in substrate 2110 where a body of an interconnectionelement is to be formed to serve, in one manner, as an electroformwhereupon the body can be fabricated.

FIG. 37 shows structure 2000 after a planarization procedure such as achemical-mechanical polish to planarize first conductive material layermask 2150 and the tip structure. A planarization procedure establishes,in one aspect, the height of the tip structure.

FIG. 38 shows structure 2000 after the introduction of second maskingmaterial layer 2160 serving as a pattern for a body portion, such as aleaf portion, of an interconnection element. Second masking materiallayer 2160 is, for example, a photopolymer such as a negativephotoresist. FIG. 38 also shows the introduction of first body material2155 a over surface of substrate 2110. In one embodiment, first bodymaterial 2155 a is a conductive material introduced by an electroplatingprocess such as an electroplate alloy of nickel-cobalt. First bodymaterial 2155 a is introduced to a thickness approximating the thicknessof second masking material layer 2160. It is to be appreciated that theamount deposited and the thickness of first body material 2155 a willdepend, in part, on the desired thickness of the particular leaf portionof the body of the interconnection element being formed.

FIG. 39 shows structure 2000 after the removal of second maskingmaterial layer 2160. In the embodiment where second masking materiallayer 2160 is a photoresist, the material may be removed by etch, laserablation, or wet etching.

After the removal of second masking material layer 2160, FIG. 40 showsthe introduction over the surface of substrate 2110 of second conductivematerial layer mask 2170. In one embodiment, second conductive materiallayer mask 2170 is a material similar to first conductive material layermask 2150, such as copper introduced through an electrolytic process.

As shown in FIG. 41, after the introduction of second conductivematerial layer 2170 over substrate 2110, first body material 2155 andsecond conductive material layer mask 2170 are planarized by way of, forexample, a mechanical polish or a chemical-mechanical polish to form aleaf portion of an interconnection element on substrate 2110. In oneaspect, planarization of first body material 2155 a and secondconductive material layer mask 2170 establish the final thickness of theleaf portion of the body (i.e., control the final thickness of firstbody material 2155 s).

FIG. 42 shows structure 2000 after the introduction of third conductivematerial layer mask 2180. In one embodiment, third conductive materiallayer mask 2180 is similar to first conductive material layer mask 2150and second conductive material layer mask 2170 and is, for example,electroplated copper. In this embodiment, third conductive materiallayer mask 2180 is introduced to a thickness on the order of 0.1 to 5μm. Third conductive material layer mask 2180 defines, in one aspect, agap or opening between adjacent leaf portions of the interconnectionelement body.

FIG. 43 shows structure 2000 after the patterning of third maskingmaterial layer 2190 over the surface of substrate 2110 and to have anopening to third conductive material layer mask 2180 at a point desiredto be utilized as a support area between adjacent leaf portion of theinterconnect element. In FIG. 43, third masking material layer 2190 ispatterned at opening 2195 to expose an area portion of third conductivematerial layer mask 2180 at a proximal end of the structure relative toleaf portion of material 2155 a.

FIG. 44 shows structure 2000 after the removal of the exposed portion ofthird conductive material layer mask 2180. In the example where thirdconductive material layer mask 2180 is copper, a wet chemical etchingprocedure may be used to remove the exposed copper.

After the removal of the exposed portion of third conductive materiallayer mask 2180, FIG. 45 shows structure 2000 after patterning thirdmasking material layer 2190 a second time to have an openingcorresponding with an opening for a desired second leaf portion of thebody of an interconnect element. FIG. 46 shows the structureintroduction of second body portion material 2155 b over the surface ofsubstrate 2110 in the patterned opening of third masking material layer2190. In one example, second body material 2155 b is similar to firstbody material 2155 a (e.g., Ni—Co) and is introduced by an electrolyticprocess. As illustrated in FIG. 46, the leaf portion formed by firstbody material 2155 a and second body material 2155 b are separated bythird conductive material layer mask 2180 with the exception of asupport portion.

FIG. 47 shows structure 2000 after the removal of third masking materiallayer 2190. In the embodiment of third masking material layer 2190 is aphotoresist, suitable removal methods are discussed above.

FIG. 48 shows structure 2000 after the introduction of fourth conductivematerial layer mask 2210. In one embodiment, fourth conductive materiallayer mask 2210 is similar to the previously introduced conductivematerial layer mask (e.g., copper) and is introduced by an electrolyticprocess.

FIG. 49 shows structure 2000 after the planarization of fourthconductive material layer mask 2210 and second body material 2155 b. Theplanarization step defines, in one aspect, the thickness of second bodymaterial 2155 b.

FIG. 50 shows structure 2000 after the repetition of the aboveoperations to form three additional leaf portions and post 2200utilizing alternative operations of pattern mask, conductive materiallayer mask, and planarization. FIG. 51 shows structures to leave afree-standing interconnection element. In the embodiment where thevarious conductive layer mask are formed of copper, a wet chemical etchprocess, selected for copper may be utilized. FIG. 51 shows structure2000 including interconnect element having a tip structure coupled to abody portion of five leaf portions of first body material 2155 a, secondbody material 2155 b, third body material 2155 c, fourth body material2155 d, and fifth body material 2155 e. Coupled at a proximal end ofleaf portion defined by fifth body material 2155 e, is post 2200.Following the removal of the conductive material layer masks, seed layer2130 may be removed such as by an etching step as known in the art toexpose release layer 2125. FIG. 52 shows the structure after the removalof the exposed release layer 2125. At this point, the free-standinginterconnection element may be transferred to, for example, anelectronic component similar to the transfer described with respect toFIG. 17 e and the accompanying text.

In the above embodiment, an interconnection element is formed on asacrificial substrate and then transferred to an electronic component.It is to be appreciated, that the techniques described in thisembodiment of forming an interconnection element on a sacrificialsubstrate is again representative of one technique of forming theinterconnection element of the invention. A second technique wherein theinterconnection element is formed directly on an electronic component isalso contemplated. Reference is made to patent application Ser. No.09/205,022, filed Dec. 2, 1998, entitled “Lithographic ContactElements,” and patent application Ser. No. 09/205,023, filed Dec. 2,1998, entitled “Lithographic Contact Elements,” claimed by the assigneeof the invention described herein which describe such a technique andare incorporated herein by reference.

Still another embodiment of fabricating the interconnection element ofthe invention may be accomplished utilizing a process described by AdamL. Cohen, in an article entitled “3-D Micromachining by ElectrochemicalFabrication,” in the publication “Micromachine Devices,” Vol. 4, No. 3,March 1999 at pages 6-7. The article describes a selectiveelectroplating process utilizing through-mask plating. Specifically, aconformable insulator is patterned directly on an anode and pressedagainst a substrate to establish the electroplating mask. Afterelectroplating, the mask is separated from the substrate. In the instantinvention, one use of the process described by the referenced article isto substitute the conformable insulated mask for the masking materiallayers and pattern the primary interconnection element components.

Various embodiments of the interconnection elements disclosed above areparticularly suitable for making electrical connection with, forexample, an electronic component having “fine-pitch” contact pads orterminals, for example, spacing of at least less than 5 mils (130 μm),such as 2.5 mils (65 μm). Applications to larger scale devices,including devices with contact pitches of about 50-100 mil (1.3-2.6 mm)and even larger are feasible as well.

In the preceding detailed description, the invention is described withreference to specific embodiments thereof. It will, however, be evidentthat various modifications and changes may be made thereto withoutdeparting from the broader spirit and scope of the invention as setforth in the claims. The specification and drawings are, accordingly, tobe regarded in an illustrative rather than a restrictive sense.

1: An interconnection element comprising: a first resilient element witha first contact region and a second contact region and a first securingregion; and a second resilient element, with a third contact region anda second securing region, coupled to the first resilient element throughrespective securing regions and positioned such that upon sufficientdisplacement of the first contact region toward the second resilientelement, the second contact region will contact the third contactregion, wherein the interconnection element is of a size suitable forconnecting two electronic devices. 2-83. (canceled)